Revell 1/48 A-10.
Not being happy with the kit HUD I decided to try to improve it. It had a simple divot under the combiner glass where a convex lens should be. My first attempt was to try to create the lens with a ‘bubble’ of clear glue. Neither Testor’s ModelMaster Clear Parts Cement nor Super Glue Gel worked to my satisfaction.

Using the ol’ pin vice I drilled out the lens orifice. In my stash I found a length of clear sprue of the proper diameter. I sanded down one end to a passable convexity, stuck it through the hole to measure the depth, cut it to length, painted the far end light green, slid it in place and ‘painted’ a drop of Future on the visible end.

Voila! A simple way to simulate a HUD optics lens.

Remember—this will work on the original F-16 A/B HUD, F-16 Block 25/30/50 WAC HUDs, A-10s, and some other aircraft, but F-16 Block 40 DO HUDs, the F-22, et al have a flat piece of glass under the HUD combiner.

Keith