There's quite a few that just use Gorilla glue products. The original epoxy product call out can be found on the Winnebago 'Adhesive' pages for your rig. Many completely sand down the surface and follow epoxy practices to reglue the brackets. This type of issue is very common with Winnie RVs so there's lots of threads about it.
What I would do is drill holes through the bracket's holes through the body apron as you call it and use flathead SS screws from the front. Size 6-32 with self locking nuts. That way you never have to mess with messy epoxy or prep for it and the screws will likely last as long as you own the rig. You could also use 8-32 hardware if you'd rather.
Here's my ad free articles about how I did a similar job on my front and rear brackets:
Body Work...
I fully expect to have to work on the headlight brackets here eventually, so far they're holding fast.
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Linear Mode
