Hi, and thanks, Welcome to the forum!
When you say extend the image inside the bezel do you mean having the background image appear inside the bezel? But behind the frame?
Could you include some images of what it looks like when you had it working the way you want? And could you include an image of just your overlay that you are using? This stuff might help me figure out what you’re after and if it’s still possible, or if we need to adjust something.
Thanks for the quick answer!! If I’m not mistaken, there was an option called 2D extended curvature. It allowed to extend the game image (while automatically reducing the length of the bezel) but without affecting the frame edges. In my case, I like to keep the vertical bezel edges wider than the horizontal ones, but I have misalignment of the reflections in the corners. I can correct the reflex by enlarging the bezel horizontally, but I completely lose the edges of the frame. So what I have: Desired bezel edge, but misaligned corner reflections or Reflections alignment OK, but no frame edges.
I wish I could change everything in the bezel without affecting the frame at all.
Thanks for your time!
I hope attached images can help.
Ok, I think I understand, is the main issue that the reflection in the corners is not aligned?
If so you can adjust the roration of these highlights with some parameters near the end of the list called [REFLECTION CORNER ROTATION] Offset Top & Bottom to correct the highlight.
Let me know if this fixes your problem, or if you are looking for a something else 
Edit:
After re-reading your post again it seems that because at least part of the frame is actually in your top-level image or overlay image that you would like the option of managing the frame scaling completely independent of the tube scaling, so you could adjust the tube & bezel without affecting the frame.
Let me know what you think
Remi you are right. I managed to correctly align the reflections in the corners. Thanks! Do you intend to return with the old option that I mentioned in the previous post?
Yes, it would be interesting to be able to resize the bezel and tube without affecting the frame.
Couldn’t this already be done by adjusting the bezel height and width so that a bit of frame shows? (Don’t these parameters already provide independent scaling?)
Right now the bezel & frame size is relative to the tube/screen size, so if the tube gets bigger then the bezel and frame get bigger to accommodate the tube.
What a feature like this would be helpful for is where you have a static image which needs to line up with the frame somehow, and you want to set the frame size, then adjust the tube size without affecting the frame.
I’m still not sure how many people are using it in this way
This is exactly my case, since I use overlays outside the standard measures.
I’m fairly certain this can be done using existing parameters. Can I ask you to post the overlay you are using?
Yes, it is possible to make all the adjustments currently. Making the adjustment of the bezel and tube independent would be perfect.
Usually overlays are made to measure (4: 3 for most systems). But I created ovelays without worrying about measures. The game image area has an approximate value of 1632x1248. See image:
Looky here!
How close are you to your TV?
Probably not handy as doing something within Retroarch, but if it helps, I might be able to help with an AutoHotKey script…
AHK scripts are pretty useful to modify text files, eg: manipulating an .slangp or a .cfg. Or even, copying/pasting files (like having a folder with profiles to copy and paste over the current loaded).
The downside is that the user would need to have AHK installed to run the script, or have one .exe running the compiled script.
Mega Bezel is updated to V 2020-08-10
Changes:
Retroarch 1.9.0 is required because the shader now leverages increased maximum number of parameters, textures and shader passes
Presets have been renamed slightly
All presets (Including Royale) now include Dogway’s awesome color correction shader Grade!
Most of the old color correction has been removed and is replaced by grade
Fake scanlines to respect vertical scanline direction
Tube Glass Image Scale, scale the reflection on the tube glass
Documentation added for most Parameters in shaders_slang/bezel/shaders/HyperspaceMadness/Mega Bezel Readme.txt
Performance of Guest-Venom Preset on Nvidia RTX2060: * 3840x2160 - 155 fps
Mega Bezel Still to Come:
Nice update!
An ambitious list! I have learned to expect nothing less. 
Hmmm… I wonder how I can use this. 
You’re the best!!!
Thanks, I really want to thank @Dogway for the awesome work put into Grade, it combines so much great stuff! And integrates a lot of knowledge about how all the signal & color transforms work and make it really useable.
Hey HyperspaceMadness , in addition to performance, could you show the visual difference between 2D and 3D curvature settings? Some images would go well!
Awesome work as always. So many options on this shader. Curious if it’s possible to get those scanlines on higher res games to follow the screen curvature and if not perhaps a toggle to auto turn off the curve?
Thanks Yeah, now that there are more parameters available I’m going to revisit the “fake” scanlines and make them more like the mame-hlsl, and I’ll add a parameter to control how much they curve.
I could post some comparisons, but the best way to get a feel for the difference is to try it out interactively.
The biggest difference between the 2d and 3d is only 3d can do tilt, 2d is also much faster, also if you want extreme curvature 3d does a better job.
@HyperspaceMadness I think your fake scanlines method might be better than the mame_hlsl. With mame_hsls a psx core resolution of 2x the scanlines work at 50% scale. (4x is 25%) On Dreamcast I have to set it to 49%. The Bezel shader seems more consistent on multiple resolutions.
