To mount a flat object to a curved surface, you need to build a mount to bridge the gaps between the two. I also wanted to make it look nice, neat, and factory, so making a slightly flared mount or "plinth" is a must.
I started off with some balsa, cutting it slightly larger than the rubber gasket.
The next layer is slightly larger still and the two after that are even larger, but only quarter size. I did that to lessen the amount of sanding and shaping I would have to do later. I may need to add a 5th layer to help the top and bottom, but I won't know until I trial fit them.
A little epoxy and I have some very rough mounts. I will still need to add more epoxy, filler, and glassfibre before I sand them all smooth.
While I still had the epoxy in a cup, I decided to roughly do the round mounts for the turn signals. These are round amber "beehive" style lights from the MGA and Bugeye Sprite, so they need round mounts. Thankfully, I had a cardboard tube laying about that was the perfect size.
A little cutting, some balsa circles, and epoxy later, I have capped tubes.
Yes, it is still all very rough, but filling, sanding, and polishing will take care of that. Unfortunately I have a busy work week ahead of me, so it may be a few days till I can get to them again. All the more time for the epoxy to harden up properly