I used to have a share in an early Std Cirrus (pre-washout change)
that had a particularly difficult case of poor low speed aileron
control and we used the open airbrake technique as well as lots of
rudder to keep the wings level. Many years later a friend and I
rented the same glider for a year and my friend put mylar seals over
the top and bottom surface aileron gaps (instead of the original top
surface only tape) and also installed mylar rudder seals. To my great
surprise the ground run aileron control was greatly improved -
transformed in fact - not only that but it changed from being a
vicious little spinner to rather benign at the stall.

I suspect that it is something to do with the large draggy lower hinge
line gap when the aileron is at full up deflection.

John Galloway