I recall hearing many years ago about undesirable flight characteristics of the Rutan Vari-Eze when the laminar flow canard got too contaminated with bugs and b

I recall hearing many years ago about undesirable flight characteristics of the Rutan Vari-Eze when the laminar flow canard got too contaminated with bugs and became very nose-heavy. A solution adopted by many owners was to put micro vortex generators on the upper surface, which wasn't great for the laminar flow, but maintained predictable flying characteristics irrespective of contamination. That had potential risks, though, because the airplane was designed to have the canard stall before the main wing, which would lower the nose and prevent the main wing from ever stalling - eliminating the possibility of the stall/spin accident. Adding the vortex generators could change the aerodynamics enough to the point where the main wing could be stalled before the canard. At that point, since you have no downward-lift-generating tail surface, breaking the stall can be difficult and you could end up in an unrecoverable stable "deep stall". Now there are cases where you can see vortex generators on both the upper and lower surfaces of some control surfaces, as on the Quest Kodiak, to provide better low-speed authority in the wing stall regime.