I think your main problem is that when doing an elevator you do not "feed in" the elevator. You pull full deflection and hold. Feeding in the elevator promotes flying on the edge of stall, where most planes will have a tendancy to porpus or snap. Same generally applies to a harrier.


Of course if your cg is not far enough aft, it will be impossible to do an elevator, you won't have enough elevator authority to keep the wing fully stalled. My judge for the correct CG is to perform a 45* inverted climb at about 1/2 power (enough to sustain the climb without accelerating). Let go of the elevator, the climb angle should slowly diminish (I would say the plane should return to level flight after about 2-3 seconds.)