Instead of PLA, have you considered HIPS or Nylon? We print with both and they offer many advantages over PLA (or ABS). The HIPS is lighter than PLA and very rigid like PLA is, and nylon is both lighter and stronger than PLA. Depending on the type (we have Taulman 618, 645 and Bridge) can be somewhat flexible which might be an advantage in the UAV application, just as it is in many of the other applications we build with nylon. The main issue with nylon is getting it to stick to the bed, but we've learned a number of techniques to get past that. One of the cool things about both HIPS and nylon is that you can sand them. Obviously, anyone who has tried to sand PLA has learned that you just get a gummy mess.