Hi Ed,
Just to be clear (for me), you initiate a bank then neutralize the ailerons and the Arrow continues to roll. Is there any slop in the aileron linkage? Are the ailerons sealed (no gap between the aileron and the wing)? I actually had this problem with my first Arrow; the cause was a bad RX which let the ailerons drift - this was more than 30 years ago. Does the Arrow show any rolling tendencies when in level flight (upright or inverted)?