I've flown with several ex-CFS instructors/examiners over the years for both FI and FIC work and recall asymmetric flap effect mentioned a number of times with the recommendation to avoid configuring flap in turns in light aircraft. 15 to 20 degree bank angle limits in climbing turns was also recommended to preserve climb performance, lookout and speed but again, in light aircraft and for teaching inexperienced trainees. Up to 30 deg level and descending turns however would be usual in the circuit if I recall.