Hi there,
Another vote for plain old polyester resin here, I can't see any massive benefits in making things more complex than they need to be in that area. From memory (always dangerous these days
) I think it's a plain aluminium bobbin in that location, just something to take the compressive stress of the bolt without damaging the fibreglass.
I'm not sure how I'd tackle that repair. I think on balance I'd build up the fibreglass first without a bobbin, taking the repairs along the horizontal section for 1-2" into good material and also up the vertical wall for the same distance using chopped strand mat. Once it was up to around 1/8" or more I'd line up and cut a hole for the bobbin, which you could align with a bolt while fixing it into place and you'd be certain it was flush with the chassis as well
As Mike says, cleanliness is the answer for a good bond, all the old paint needs to come off and the overlap area needs roughing up a touch. I use a wire brush on a drill and acetone for cleaning as it will soften old resin slightly and does make for a good joint.
I don't know about the US, but over here in the UK it's far cheaper to buy resin in 1 gallon tins from boat builders, etc, than small lots from the auto-shops. I generally use 2 types of glass matt, 300gms/sq M chopped strand matt for building up thickness and something called "surface tissue" or "veiling tissue". The latter is very thin glass, almost like a paper tissue and is used for making a neat surface over the repair. (I also use it for repairing gel coat cracks rather than body filler.)
I'm doing some body repairs on my Elan at the moment so I can take pictures of the materials in action if it's any help.
Brian
