Building L2 rockets up to 4" only to this point, I've used BSI exclusively and had ZERO issues with that product. I use the 30-minute variety (to me it cures stronger than 5-min or 10-min) on centering rings, fin to motor mount and centering rings, internal fillets, aluminum tubes for my AV sleds, bonding coupler inserts to couplers, and more. The only thing I don't use BSI epoxy for is external fillets - haven't moved from using Fix-It epoxy there due to its ease of shaping after cured. I have had a a couple of external fillets crack (hairline cracks) when something went wrong like a motor failure on a 4" Patriot last year, but otherwise this works in my building and I'm very happy with the results.