Center hole is just a hole. If you look at pics of the real cars, they usually have several unfilled former attachment points and such. I suppose I could stick a rivet in it.
The Fibersteel plastic screen is made to lay over and cover the mounting holes from the glass Speedster screen, so there's your fitment. You can just see a couple riv-nut edges peeking out from under the leather gasket on the right of this pic.
The tricky bits are the mirror and tonneau snaps. I just drilled a hole where I thought the mirror would look and work well, and then found the mirror that came with the plexi screen was a tad too tall, when stood upright as intended. It may be possible to just machine more threads up the stem to sink it; I opted to grind the top retaining nut at like a 15-degree angle and make a matching angled collet for underneath.
The one Tenax stud I had installed, using the tonneau itself as a guide before any windscreen was attached, had to be relocated about an inch rearward in order to get enough headroom for the snaps to function (you can see that hole too). I also had to have the tonneau altered likewise.
DM'd additional pics.
Thanks Ed. Took a brief look at your post, but I’ll take time to digest it later. I’m on my way down to change screens myself. Like yours, I have both sets of holes. My car had the lexan screen on it when I bought it and I had Carey et al put the Speedster screen on in preparation for my drive to NYC.
But, like Carey warned me, the header is right in my line of sight. Now that I’m driving the car a lot, it really bugs me. I find myself slouching down in the seat to see under it which inevitable starts hurting my back.
I’ll get to the mirror later. Checking the dimensions of that Cobra mirror someone suggested, it may be too tall. But I found one on Moss motors for a TD or TR-3 with a shorter stalk that might be perfect, as long as the angle will clear the clamshell.