I have the exact same problem, I just got two aimtrak gun and I am trying to make the second player work with the second gun. If i am playing with one gun it work fine, but I doing anything and I can't fine a way to make work the second gun for the second player. I am on Windows 8.1 with mame .159. I have the same mame config from the .153 tutorial of this thread :
I have the aimtrak utility and my first gun have ID 4 and my second gun have ID 5 and both trigger working in windows and they are both well calibrate as explained in the instruction manuel from aimtrak website.
When I go in mame and I try for exemple Area-51 Maximum force or Operation Wolf 3, my two gun are seen as 2 blue target that I can move separatly with each gun. If I hit TAB and go in player one and player 2 config for Button 1 and I hit trigger button of my guns, each gun are seen as GUN 1, it think that my two gun are the same gun. If I hit F2, I can do the test for both gun, and I can start game for both player, each player is able to move the target, but if a player hit the trigger, it fire for both player at the same time.
Is I am doing something wrong, or I need a different config for mame .159 or it's a problem with the aimtrak gun and Windows 8.1?
Thanks you in advance!