Duck Hunt with Mame and Aimtrak

[Menteith]

Hi, am new to this board. I recently bought two Aimtraks and have them hooked up to a 120 inch projector. Works very well, and I can even stand reasonably close to the screen (around 3 meters with the LED lights pointing downwards diagonally).

I already tried the guns with some games in Demul, M2, M3, and so on, and everything works pretty well.

Yesterday I wanted to try out Vs. Duckhunt on MAME. I have followed all the instructions for setting up MAME for the Aimtraks following Marc's instructions on his webpage. In Duck Hunt, however, the shooting itself seems not to register. The target reticles move accurately where I point them, and even when I pull the trigger, the screen flashes white, however the shooting itself i not registered - that means I cannot even shoot the Player 1 and Player 2 selection at the beginning of the screen. Is there anything I am doing wrong ?

Thanks!