I fixed it this morning. Here are a few pictures.
The roof would stick at around this point on opening. It would carry on a little more but would clearly be stuck against something.
The problem is the cross bar connected to the bracket which is vertical in this picture.
It pivots freely but is actually supposed to be pulled backwards during the opening procedure. In fact if you stop the roof opening at this point and push it back to this position by hand, the roof will probably open OK (just this once).
The bar is supposed to be pulled back by this piece of elastic, one on each side of the car. It’s the piece I’m touching with the scissors. This elastic perishes over time and doesn’t pull the bar back.
I actually have three pieces, from previous repairs carried out before I owned the car. The piece that looks like a seatbelt, which I’m not touching, is a critical part of the roof and definitely must not be cut
.
Unfortunately, the last repairer didn’t sew on the new elastic, but riveted it on. This made it very awkward to remove the old pieces, which I did very carefully with a Stanley knife. I also had to cut away the original stitching.
Ideally you would sew new elastic in place of the old. With the rivets in the way, I ended up cutting small slots in my new elastic strips and hooking them onto the rivets. Naturally in my excitement to take it for a test drive I forgot to take a picture but I’m sure you get the idea.
Hope this is useful to anyone struggling to work out where the elastic bands in a Spyder roof are and what needs replacing.
Edit:
I originally used dressmaking elastic etc. for waistbands. I doubled it over to get a bit more strength. 5cm was slightly too wide. Anything from about 3 cm would probably be fine.
Another edit:
I found that elastic wasn’t strong enough, so I switched to 3mm bungee cord. It’s surprising how taut it needs to be. I took advantage of the rivets. Not a neat job I know, but I guess it won’t be seen.