Well, I think I did something stupid....

in order to put weight at the front, I epoxied some pieces of metal to the plastic engine mount... right between the engine and the fuselage.... I put LOTS of epoxy and it looks like rock.... but I did not think that the muffler and engine are very close (not touching, maybe 1" of space)..... is the epoxy going to melt or something like that????? or I should be fine???