strengthening abs interior panels

My 94 caprice has rather flimsy and squeeky interior panels. Its rare to find one with good door panels, most of them crack in several common areas. I'd like to beef up the door panels and maybe a few others. I just dont know how or what I'd use to strengthen ABS plastic. Ive heard fiberglass is not a good choice, but Ive heard of others using it.  I did a little searching and didnt find anything about strengthening interior panels.

Any help or suggestions would be appreciated.

Sometimes (depending on the shape) a spray on sound deadener will help. Try Cascade Audio or Dynamat. Once dried & hardened it will decrease the resonant frequency of the panel and help with brittleness. Also, instead of fiberglass per se, only use the resin and hardener and a thin coat should keep the panel where you want without warpage.

Good luck