Use this material, I Used it on a Fresh out of the box P3P before ever flying it This stuff is like Steel, Super strong an easy to use, mix it up thin and pour it around the base of each moor mount area to a thickness of about 1/4 inch, just short of the screw holes for the motors. Allow it to harden an hour and it will become super bonded to the body shell. It is Miracle material, guarantee never a stress crack. Plast-aid® multi-purpose repair plastic for your repair solutions.
I assume this is a plastic powder maybe ABS or Styrene with solvent?