The New Mayflash Wii Classic Controller Adapter

Has anyone tried to use ‘The New Mayflash Wii Classic Controller Adapter’ http://www.mayflash.com/Products/NINTENDOWiiGC/PC052.html with Retroarch? If so do I need any third party software to use alongside this for button mapping etc. or is there a write-up of any kind? Thanks in advance.