Join Date: Jan 2018
Location: Greenville/Raleigh, NC
I opted not to de-rim my 40b...Ive had a flooded basement once before and it sucks. Every pane of glass and tank are different...you may have gotten a friday 5pm special and not have a good experience.
IF you still ago ahead with it I would only do the top, you are just going to see substrate up to that point anyway and it would give me a little peace of mind.
As for the brace I would add one about 2-3" wide in the center. The corners will only really give you strength in the joints but any bowing in the glass is going to happen at the unsupported (or bonded) part and that is the center of the glass.