Im REALLY suprised no one else mentioned this.

My $$ is on your elevator setup. check them for flex. I ended up ditching the pull/pull system they used and put 2 servos in the tail becuase i found it almost impossible to get the flex out of the control horns.

At certain attitudes and high loads, they WILL flex, and it will snap to the weaker side, everytime. yours does the right, mine was the left.

Best way to test this. Come by for a low pass at about 1/2-3/4 throttle. chop throttle to idle and pull into a wall. If it tips when going into a wall your elevator halves either are not matched or flexing. This is only accurate if your plane is laterally balanced as well.

Ther stock horns that mount onto the aluminum tube for the elevators suck, they flex like mad. I could hold one elevator 1/2 flat to the tail, and move the other side to full deflection they would flex THAT much.

Decent plane, i have a YS .63 on mine with a 13x4 prop, really fun for a mix of pattern and mild 3D. but lacks in many areas of 3D performance.

Airframe itself is nice, but goldbergs hardware for the plane is piss-poor, and that's being nice about it.

Even if you feel it's flying better now, check those elevators for slop, i have yet to see a matrix without issues with the setup back there.