I'll bet you dollars to donuts these airplanes are all built with a little bit of right thrust. That helps offset torque when upright, but actually assists torque when inverted. In other words, if the torque wants to pull the airplane left with a value of 1, the right thrust has a value of 1 which cancels it out, resulting in a left pull of zero in upright level flight ... but flip the airplane upside down and you have a left pull value of 2.

The fixes are:

1. Remove the right thrust and re-trim rudder and ailerons,

2. Tape some spare change to the left wingtip and re-trim rudder and ailerons, play with the amount of weight until your inside and outside loops act the same, or

3. Just live with the fact that to do an outside loop that's straight, you will need a shade of left rudder and a shade of right aileron.

Duane Gall
RCPRO