Awesome Jeff! Just found this thread(D'oh!), been drooling over your FB pics though...
But anyway, the shifter talk reminded me of DareDevil's V-twin Excelsior's solid linkages, you should check them out. See what you think of them over a dual cable driven (upshift/downshift) system. It's a lengthy thread, but he gets into some good detail w/pics around here
. With a solid linkage you could use trigger/thumb, or even a twist grip if you wanted to.
Plus it'd feel more solid than cables too eh?
Just another thought for the pile