Differential shouldn't make it pitch down in a roll it will just be the wing tips and the nature of the bird ... it won't roll like a fighter. Aim the nose up before you do your rolls and use a little rudder as well. Kinda like a snap roll but don't be too enthusiastic or you will take it home in a box. About 30% differential should be enough.
At slow speed the AXN WILL
tip stall on a turn - it won't fly under a fast jog pace so at low altitude make sure you fly it.