..and that's pretty much there is to say about it.
First, after making a template, you need to cut out tree pieces of plexyglass. The gun body itself, the 'bolt' and then the trigger. The bolt have to be either bended at the back like I did, or it can be done by 'sandwiching' a little piece between two 'side pieces', but it will increase visibillity because of the screws, wich is bad, or glued, but it might make some bubbles in between.. It's your choice..
Then with a drill-press, remove material where screws will be fitted & the area for the trigger. Beside making the assembly possible, it also removes some stuff so it's even more invisible.. Use fine grith sandpaper to achieve a nice & clean finish on the cuts and with a butane torch it is possible to clear the plex = even more invisible... wow....
Assemble with two coarse thread screws. I would have used plastic dowel-pins but I'm not sure if they'd be strong enough. A broken gun is not an option when you're in the action.