@Zombeaver has done some 2 and 3 screen presets.
https://forums.libretro.com/t/zombs-mega-bezel-pack/39519/31?u=duimon
Unlike the question in the post you referenced, he uses a single bezel which is more true to the original. I doubt anyone wants to play Darius on three split screens with bezels.
Yeah like Duimon mentioned, for games like Ninja Warriors, Warrior Blade (Rastan 3) and Darius in my experience the single super wide screen is the nicest presentation.
For something like TX1 or BuggyBoy it could be interesting to separate the screens and add a perspective tilt on the side screens since in the original arcade machines they were tilted and acted kind of like windows in the car. But that’s a fair bit of work for one or 2 games.
I do wonder if some sort of perspective projection of a wide curved screen might look nice, although at that point you wouldn’t want it to look like a tube anymore.
I’ll check out Zombeavers, he has some nice ones.
I tried a couple dual screen games… I made one for Spy Hunter 2 that turned out ok, and then tried Cyberball, but couldn’t get the screens right. There was always a problem with the gap in between… so then I was wondering what people had done for other multiscreen games with no gap.
Let me know if you want to take a look at this again and maybe we can figure out a solution to the problem.
Thanks… mainly it was when I had placed the screens as close together as the “position offset between screens” would allow, then I had trouble placing the screens (I was trying to make a side-by-side horizontal) because you can only move the second screen in the dual screens section, so I was going back and forth between that and the offset and position settings at the top for the first screen to make small adjustments, but the adjustments to the second screen would end up causing me to make more adjustments for the first screen and eventually I gave up.
The question I started having as I was working on these is… I’m really only playing these games single player… would it be better to disable the second screen on the 2 player vs. double screen games? If I do, then there’s the question of authenticity, but I think playability overrides that for me. If I do decide to eliminate the second screen… I’m not even sure if there’s a way to handle that in the shader (total noob feeling his way in the dark here).
Anyway, here’s a screenshot of my Spy Hunter 2 just for fun.
So the best way to do this for this example would be to increase the cropping on the right side to probably 50% then poof! no more second screen 
.
Just found this:
He’s got a thread here. He’s been churning out the presets.
Worked perfectly. Thank you.
Hi! I’ve got something weird happening with a couple of cores, so far the Beetle HW PSX and the Flycast Dreamcast cores. On those, the side bezels on both TheNamecs and Zombi’s shaders are reversed and inverted. I’m running the latest version of RA and have the most recent update of Slang shaders.
Is there something I need to tweak on the parameters?
You need to change the [FLIP & ROTATE] >>> Flip Viewport Vertical parameter from 0.00 to 1.00.
This is a common issue with hardware rendered cores.
I am not surprised you are getting the error with @TheNamec’s presets, since his aren’t tailored to the core, but Zombi must have been using software rendering or just didn’t check it live. 
In any case, make the change and save a core preset.
just thought how great a “passthrough” core where that could grab the image of another screen/app and display that in retroarch to throw everything at this shader ^^
besides…
HSM…we …urgh…the arcade shot em up fans …ähm tbh… I would like a third screen option
why ?? cuz Darius 
(and this could improve the idea to use screens as lightsource for overlay stuff leds,etc.)
This has been discussed again recently. While it makes sense on paper it doesn’t make sense in practice. Darius and other similar games use border-less screens so the screens appear as one.
Having three bezels, even with no gap, would not be enjoyable or accurate.
One solution for flashing lights etc. would be to have a random brightness timer on a layer and use it for these elements. (If this is even possible.) If it doesn’t need to flash you can just bake the lights into the graphic.
Some things the MAME core is capable of, with it’s layout system, the Mega Bezel will never be able to do.
…unless some method was developed to allow it to interface with those additional MAME modules which drive special off-screen features at some point in the future.
yeah i know ^^
about the mame capability hsm once said he has something like this on his list …for someday but for that an entire driver has to be coded …i´m not so the coding guy so idk.
but i like your timed idea for brightness. this could also simulate a couzy window with some lightnig/thunder at night .
but tbh everything else is luxury anyways ^^
i´m happy with that what we already have …hsm already has a lot of amazing ideas still in mind for it so am happily waiting
Not even the RA layout feature supports this, so while it’s possible, even making that happen first wouldn’t allow the Mega Bezel to take advantage of it.
Seriously… we would need an image layer for each and every element… sometimes twenty independent LEDs.
I don’t think it needs to happen. At the very least it should be at the bottom of the priority list.
another feature i could imagine would , to setup “fakes” screens but this would also be just for overlay improvement and it would require that gif files could be displayed .
example image
if the left and right cab´s screens could use a gif that would be used as image for a screen it would improve the feeling an look for such overlays through the roof 
but it´s just another idea , not a useful one but i think it would be a striking visual upgrade
Could be interesting, if we did it we’d probably need to turn the gif or movie into a sprite sheet with frames, then we would play back the frames inside the sprite sheet. The frames would need to be core res, e.g. 224p. The sequences would probably need to be somewhat short so that the sprite sheet is not enormous.
I’m not sure if GIF support would ever be added to Retroarch to automatically as it adds complexity.
To have it on as a second screen means we would need extra dummy screens which would be possible. It would also need to add a crt effect to the dummy screen, which wouldn’t probably be too bad either, probably use GDV Mini since it can be calculated without any previous passes
to split the frames of a gif wouldn´t be a huge amount of work ^^ and i would simpley record it myself in the needed res.
maybe just the spritesheet even would work , if the recorded footage also captures the bezel effect, but that would result in huge sprites …
if its short or not isn´t the problem at all i think just make sequence loop than its not distracting at all i guess , and for some arcade thats all whats needed ^^
and yeah that is what i thought to give the dummy screen/s a simpler crt effect , glow and reflection as the main screen
if you ever think about to work on this i will happily help testing this and make the sheets etc. 
than i can help at least with something with my lack of coding skillz 
So the way I’m thinking the sprites would just be like images from the core, e.g. 256x224. The reflection would be auto-generated like we do with the main screen. I think this is probably the only way to have a consistent behavior which would be easy to set up, and also have the smallest spritesheet possible.
I’m also thinking about possibly having a spritesheet to mimic some light coming from the rest of the arcade as well.
Great! It’s always awesome to have a motivated beta tester! I’ll let you know if I ever manage to get to this.
