Lars,
Fit wedges on the leading edges at the wing roots to force a root
stall. Some WW2 era military trainers tip stalled to enhance training
experience and the root wedge fix is used to remove the characteristic
(and surprise) for civilian warbird use.
Albert

(drake) wrote in message om...
Any help/advice/recollection of previous such problems and what you
did to fix it will be greatly appreciated.

Lars