I had left the fibreglass sheets to dry overnight - I have learned to my detriment never to rush working with this stuff! I laid each one over the hole where it was due to fit, and drew the shape of the hole on the back side using a Sharpie. The oscillating tool was put to good use again, and made short work of trimming the pieces to size. Once done, they were offered up to their respective new homes. More trimming was needed until each one fitted with minimal clearance. These were taped into place, and I flipped the headlining over before fibreglassing them into place from the back. They're now drying.
Once I'd finished doing my fibreglassing thing, I completed a job that I've been meaning to put right for AGES. The driver's side indicator and sidelight combo was hanging down. Why? One of the Rivnuts had started to spin because there was a crack in the fibreglass. I had already repaired this from behind (and through the crack) using resin and chopped strand mat, but for some reason I had never completed it (probably because it has been F cold and/or raining). I also remembered that the bit where the Rivnut sat was a bit "bulgy", causing said Rivnut to sit at an angle. This was sorted by a brief tickle with the finger sander. In went the new Rivnut, and the light unit is sitting happily in its proper home. I should add that the bonus today was the front of my garage is a suntrap in the afternoon, so it was a lovely place to be. Hopefully this will continue!
Laying the new sheet over the top of the hole needing to be filled.
Sharpie marks all over the sheets
Pressed into place before fibreglassing
Like this!
Indicator/sidelight unit now in place. Picture makes it look wonky, but it's fine.
15 degrees! A welcome change!