Having both shifters will work fine, or you could use 1st and 2nd for up and down, but they won't automatically return to center which sucks.
TheSharkFactor drilled holes in the wheel and added buttons for the up/down.
I looked at his build thread, but there are no really good pics. Pretty sure I saw some on other websites.
I prefer using paddles for games that have more than 4 gears, but that can get pretty involved.
I made a paddle setup for my new dash, but I have a fair amount of money in it, it was a PITA to put together and I haven't tested it much to see if it's reliable.
Just using the up/down shifter is probably the easiest route.
The author of RacerMAME had another program that will make that shifter also work for the 4 speed games in MAME & Model 2 (Supermodel supports it without any additional programs). That way you'd only need one shifter. Follow the links to RacerMAME in the driving cab info thread.
That wasn't me who was using Hyperspin. It was mbasile35.
http://forum.arcadecontrols.com/index.php/topic,114400.msg1223406.html#msg1223406I think it's a pretty cool concept for driving cabs and would like to see a driving cab theme available for download someday.