I had a bunch of 2" strips ripped up for a Junk sail batten experiment. I was going to use them for center webs with a bunch of holes drilled on both sides to Thai lace individual sail panels between. I was going to glue dimensional lumber on the sides for rigidity. That never went anywhere, so I ripped it up for the window frames. 1-1/2" strips and 3/4" strips.
Cut a bunch to length to make the frames for the large rectangular window on each side, and got them laid out.
Alternating overlap in the corners
I'll glue these frames up solid and get them sanded and pre-painted. I'll set the Plexi into the frames with @ 1/8" clearance all the way around for expansion, and bed them in latex caulk. I'll then screw the whole assembly onto the boat, again bedding with latex caulk. A couple coats of white paint on the cured exposed latex, and the window is done.
Once again a "little job" that's going to burn a lot more time than expected. I think it will be a better job and much more professional looking than a bunch of silicone and exposed screws right through the plexiglass. Using latex caulk will let me pull the frames and change out the panes if it's ever needed. The latex is also real easy to refresh without pulling everything apart.