12 years ago I built a 4 inch Madcow BB, 54mm MMT. The parts are good quality and went together perfectly. I'm sure it's the same stuff today.
BB has a tail cone which causes problems. gotta glue it in first, before the fins, because the fins taper on it. That made it difficult to get enough epoxy in the slot for the fin to MMT joint.. and no way to do internal fillets...
I don't recall what I did for motor retention, I'm sure whatever you do will be fine.
I flew it dual deploy on larger and larger motors, warp 9 etc., until it died. K695. Fins fluttering, exhaust braided, very pretty... then the fins detached and the airframe wiped out, still under power! the altimeter fired and it all came down nicely. crowd pleaser.
but i wasn't happy, because again there was no good way clean up the root edge of the fins, and the slot, and the mmt, to get a repair glue job. all the parts got recycled, of course.