Alright I just finished testing my lightguns with the demo of trigger happy. First I'd like to say this looks like a great concept and you should definitely keep going with it! Now on to the test results...
My lightguns work decently with your test. I could hit the targets most of the time after a few shots. The reason it takes a few shots, however, is because the accuracy is not perfect. For some reason the pelican stinger lightgun (or at least the ones I own) are always off on accuracy. When I shoot at a spot on the screen, the game registers a hit a couple inches upward and a couple inches to the left. This is the same thing that happens on HOTD2 and Confidential Mission as well. This type of gun just doesn't calibrate correctly. So if you could put a hack in your code for this gun specifically to compensate for the inaccuracy then it would be great!
If you need me to do any more tests then don't hesitate to ask!
EDIT: Actually the accuracy on Confidential Mission is almost perfect, unlike HOTD2. It's only off by maybe half an inch upwards, nothing compared to HOTD2. It's the PAL version of Confidential Mission and the NTSC version of HOTD2. I doubt that makes a difference, but perhaps I'll track down a PAL version of HOTD2 to try out.