personly i dont have any stacks on my engines yet because of the cowls,and theres no problems.second,if you want to,take a peice of 1/4 inch tri-stock and tape it to your leading edge of the wing before you fly about 1/3 of the way from your fuse to the tip.this causes a sharper angle of attack on this section of the wing and it will stall first reducing tip stall.or,set both ailerons at neutral to the trailing edge as always.after this,(RAISE BOTH AILERONS) 1/8 of an inch eqauly on both sides.this creates washout and also reduces tip stall.after your familiar with your plane you can remove these two cures as neccesary or slowly.if you raise the ailerons make sure there the same.