Springfield Leather Company sells a bag stiffener called bontex. I've used it on quite a few bags. Just cut about 1/4"-1/2" smaller than your bag pieces so you have room to sew and turn out, then contact cement to your chrome. It looks kinda ugly on the inside, but as long as your lining it it doesn't matter. It won't be a a super "heavy" reinforcement but the women I make bags for don't want them to be too heavy. But this will keep your sides standing up.