Stabilization roll gain is for stabilzation only, If you want a quicker turn you should start by setting:
Bank derivative gain to 2-3 anything else is too high. I have to correct this on code .
Bank proportional gain increase! This is the parameter that will have more influence on quicker turns.
Bank integral gain This parameters should compensate for AHI missalignement so even with the AHI not perfectly aligned with the horizon the autopilot could still work. Increasing Max roll angle and Max pitch angle to the maximum(40) should help also.