Yeah, 'none' is what you what Inc and Dec to. 
You said you hacked a dualstrike joystick to make this yoke, right? Then windows (and mame) should see it as a joystick.
Well, the OP keeps saying "key" and "keystoke" when talking about the analog in stick. Keys are digital, on or off. The analog joystick is analog, a range of values. IOW, if you're changing the joystick's analog axes to keys in the joystick driver, that's your problem.
Quick troubleshooting rules for joysticks.
Does the joystick work in windows? (optional) Or in other games? Does it act analog?
Are you running any joy2key software? Are you using a frontend? (they can interfere)
Are joysticks enabled in mame? (
joystick 1 in mame.ini)
Does mame think the joystick
exists? (
verbose 1 in mame.ini, and look at the commandline)
Do the buttons work? As joystick buttons to mame?
Are the analog axes mapped to "... analog" and not "... inc" nor "... dec"?