[sabrinabellydancer]

others are more qualified to answer this, but here's my best info for a super sturdy "like iron" bra:

get a very sturdy bra one size larger than you really wear. it will shrink from being sewed and decorated.

cut the cups off the bra. at this point you can reinforce them wit denim or not. your choice.
angle the bra cups to give you the most flattering cleavage and either sew them directly together, or recreate the triangle-ish center piece out of denim. sew together with heavy duty carpet thread.

side/back pieces: i use the sugar petals side piece as a pattern and make a 2 layer side/back piece out of denim to fit me/the bra contours. make the back pieces overlap a lot on your back.

on the big overlap back area create a closure with at least two metal trouser hook/eye combos and finish the rest of the overlap with a strip of velcro. the velcro will help to keep the hooks from moving.

bra straps are also made of denim and covered with the same material that is used for covering the bra.

cover the bra with desired material. attach the straps. make necessary adjustments.

line with felt to absorb sweat and reduce friction. i do this in the belt too.

decorate, dance, have fun.

hope this helps.