a while back, I uploaded CAD files for a dual pancake mod for exactly this purpose.
here is the link for the coupling, but you have to take apart the shell and drill new holes for the standoffs, I can also upload the CAD files for the custom mounting plate. This mod is assuming you have access to a 3D printer. What this does, is essentially put a 1.5" bore cylinder on the shifting mechanism. hope this helps
https://www.dropbox.com/s/4mveor2l36...oupling.SLDPRT