Sig trainers are very light so they tend to look too big for the recommended engines. And they are very well engineered so do not give into the temptation to reinforce everything. Maybe a little 1/8" ply LG brace if you fly a rough field but that is it.

And patience is a virtue. You can save a lot of weight by using white carpenter's glue instead of epoxy. If you use a thin coat and clamp or pin, that stuff dries very strong.

If you must use epoxy to fuel proof something, mix equal parts of slow part A, part B and 90% isopropanol. Then paint on, let it soak in for a few minutes and scrape off. I let it dry and then lightly scrape with a single edged razor blade until it has a sort of even light matte look.

Tom