GRP/Fibreglass info needed

[EddyCurrent]

I don't know the answer but I imagine the strength would be increased if you also put rivets or bolts through the whole thickness each side of the lug, if that's possible in your application.

[irving2008]

Can't as need to preserve water tightness of lower/inner bit so can't penetrate it. If I could and know it was 100% guaranteed watertight I'd go that route and it'd be trivial. I need to figure out what size (area) of ali plate I need for a given force. So far haven't come up with a foolproof way to do this.

[EddyCurrent]

What about making some test pieces and applying weights to the mounting ?

[irving2008]

in an ideal world, but no time nor facilities.... was trying to model it with FEA but cant seem to get a meaningful answer...