I have it running perfectly with 2 guns. First of all you need to disable the guns in mame.ini and calibrate with the mouse. 0,0 128,128 255,255
After calibration is done then just calibrate the guns normally and you are ready to go. You have to done the same with Revolutiuon X.
The only problem with the game is that you cannot hold down the trigger and move the gun back and forth, so your trigger finger gets pretty tired after a while.
BTW, I'm running mamewah with xp also. Make sure you are using mame analog+.