ORIGINAL: Stick Jammer

What you have effectively done here is negative incidence on the stabilizer. Adding shims to the rear bolts of the tail booms does not change the wing incidence. Incidence has to be measured with the center line of the fuse perfectly level. If you level the fuse and re-measure the incidence you will see that the leading edge of the stab is now lower than the trailing edge and the wing is most likely level (0 incidence). What this has done is almost the same effect as adding some up elevator to your trim, the air is pushing the tail down in upright flight. It also has most likely seriously affected inverted flight (nose will want to drop hard because the air is pushing up on the stab).