PICOis looking great David, it's a wise desicion to use a stronger servo, HS55 gears are actually very weak ones.
Im sure you find out how hard it is to work in such a narrow fuse like this one not an easytask right?
That's why I installed aileron servos on the wings, there was not enough room for Rx AR7000, batteries, switch,fuel tank etc.

Itlooks like you'r going to finish this one soon you wont regret it, this lil missile perfomance is outstanding!!!!