i do a lot of work with 3mm thick acrylic sheets at school and we use this stuff called Plexweld. It will actually chemically weld the two pieces together. We buy it in bulk and use small needles to apply it. If your in school you should go to your shop/tech department and see if they have some you can use because you won't need very much. you will also need to find a way to secure the camera inside the box but still be able to get it out to charge and download videos.
If you could find some sort of box and drill a hole for the lens and cover the hole with lexan that may be the easiest. Just thinking you may want to be able to see the screen so you know what your filming. And make a folding mount (heartbeat sensor style public/style_extra/post_icons/icon4.gif) I tend stay away from milsim so i don't know much about rails but I think you can buy rail risers and just drill holes and run bolts horizontally through the side of the rail and the camera case.
i have the pro axis and have worn the i4's. IMO the i4s have a more stretched shape wile the pro axis has more of a square shape when looking at it from the front. i think the pro axis is better for people with a wider face
take the grip frame off and check all the magnets?(My G3 IQ has springs) and make sure you don't have any paint or debris in there. then take the trigger out of the frame and clean and re-lube everything. try adjusting your trigger.