I had a similar problem with an old MPC promo I was working on. One A pillar was broken, the other bent, and the roof had been out of shape so long it was a real bear to get back in place. I used hot tap water, bent the piece back into shape, then switched to cold water to set it. I only had to repeat this, oh, about two dozen times before the roof would stay in place long enough for me to work on the A pillars. Mine were too far gone and I ended up making new ones. Not that hard, though. I used a fine cutoff disk in my Dremel to cut an old #11 blade down to the profile shape of the a pillar. Then I cut styrene to an apropriate strip size and scraped it to shape and cut to the lengths I needed. For added security I cut a groove in the back and superglued slightly longer pieces of fine brass wire. The ends of the wire fit in notches carved into the stubs of the removed pillars and strengthened the connections.