After a bunch of scrubbing with vinegar, the old plastic of my Powerbook is looking better. Add to that my discovery of Loctite plastic bonder and things are shaping up pretty well. Among other plastic repairs, I unscrewed the heat press inserts and surrounding plastic from the hinges and reattached them to the upper case and they're looking good.

I may have to fill around them with more Loctite for a better hold. Will they stand up to repeated stresses? Hard to say yet, but I'm somewhat optimistic. This plastic bonder is some good stuff!