I do agree that "composite" (I guess that means fiberglass) would make a neater installation and I assume eliminate the bolts. I'm not the least bit experienced with glass or very handy with anything else for that matter. I'd be happy pay to have one molded. I'm sure that I could provide a paper model or accurate template taken from my tip up canopy.
Any takers?
The best advantage of using composite is laying a compound shape right where it is needed so that is a perfect match. Doing it remotely loses some of that advantage.
Once you have made a paper model you have demonstrated most of the skill required to lay up the composite yourself.
You didn't ask, but I'll offer the process anyway:
1. build up some tape layers on the rear canopy to establish your desired clearance including whatever thickness of anti-scuff tape you'll apply to the bottom of the Targa where it covers the rear canopy glass.
2. Close the canopy and cover the targa area with a single layer of clear packing tape. Epoxy and polyester just won't stick to packing tape. You can wax that as well in case you have any gaps in your tape. Should go without saying, but be sure to cover the gap between front and rear canopy!
3. Put some masking tape over the packing tape to outline the targa shape, make it about 1/2" larger than desired. Lay some plastic sheeting over the whole targa area and tape it down. Trace the masking tape outline of your oversized targa and use a sharpie to mark the top side. Mark the mid point of the strip on the top side, and mark the masking tape on the canopy in the same place to help out later. Cut this out and then use that as a template to cut your fiber layers. I used three layers of 8 Oz woven Carbon fiber. Less or more would have worked just as well, it doesn't need a lot of its own strength.
4. Lay some plastic sheet on a workbench, place your plastic strip upside down on the large plastic sheet, and saturate those fiber layers with epoxy as you stack them up also upside down. A bit of soft plastic from a lid on a container of powdered drink cut into a squeegee is a lot more useful than a chip brush for working epoxy into a fiber layer. Just pour it from your mixing cup down the middle of your fibers and spread it with the squeegee. Save yourself some time and pour your epoxy strip on the template before you drop your first layer of fiber. Try to use your squeegee to push the epoxy up through your fiber layer from the bottom. That will help you to get a good wet-out without too much or too little epoxy.
5. Put some gloves on and pick up your 'applique.' You can fold it in half, or S-fold it, or roll it if you like. I like S-folding so I can cup the whole thing in one hand as I take it to the airplane. Rolling tends to induce wrinkles. Have faith, it will unfold, and the plastic will keep the fibers from sliding into weird shapes. Don't ever try to freehand a strip of wet fibers more than an armspan without the plastic to maintain the relationship of those basic two dimensions set on the bench, you'll regret that. Then just unfold it where it needs to be. If you made mid point marks on the plastic template and the masking tape on the canopy then you can place the middle first and then just unfold out towards the sides. If you get off, just pick it up and do it again. Don't chase any stray fibers, that just causes chaos. If it gets messy just pull it off, put it back on the bench and straighten things out. If it gets really out of hand then scoop it off, toss the fiber, clean off the plastic with denatured alcohol and do it again. When you have it all there and +- 1/4" of perfect, peel off the plastic template strip, use your gloved hands to squeegee out any bubbles working from the middle outwards until it is all very smooth and tight. If need be, pull from the ends tightening the weave to take out wrinkles don't push! If you want to save some time, then let it set up enough that it has 'gelled' and cover it with a couple coats of clear epoxy. You can use some thickened epoxy on the first coat if you used a rough open weave that has a lot of texture that needs to be filled. Again, your squegee is your friend.
6. Clean up any drips with denatured alcohol. Let it cure. Pop it off, and clean up enough masking tape so you can see the joint again. Put your rough targa back on, and use some narrow masking tape to establish your desired finish shape. Then trim with a high speed grinder, dremel, whatever.
That's a lot of words, but it is really simple stuff. The end product is a targa with a nearly airtight fit over the rear canopy.