On Thu, 06 Feb 2020 22:15:11 +0000 (GMT), Dave Liquorice wrote:

use fibreglass and polyester resin to both soak in and spread the
load
using glass reniforcment on the rear

Not a bad idea, use the fibregalss and resin as a gap fille for a not
quite perfect larger bracket. Embedding that in between layers of
fibreglass.

And maybe make the bracket with fingers to spread the load through
the fibreglass. Might be easier to get a closer match to the door
panel profile as well.

--
Cheers
Dave.