A few years ago I was part of a test team gaining UK certification for a high performance microlight aircraft. We had great problems initially with very severe wing drop at the stall. Even making absolutely certain that we had no slip on at the stall, the aircraft would instantly drop a wing, not always the same one.
We tried vortex generators towards the wing tips to no avail, and changed the angle of dangle of the ailerons, again no change. In the end, we put stall strips on the inboard couple of feet of the wings' inboard leading edges. This made the stall acceptable, but to gain certification we had to include an aural and visual stall warning system.
During this process, we considered the fact that the aircraft was a two-seater with side by side seating. There seemed to be no difference whether a light tp or the standard heavy one flew the tests, nor which seat was occupied, and we began to log lateral CG as well as longitudinal on each of the test points. We could find nothing in the data to suggest the lateral CG had any effect. We also approached one of the UK's legendary test pilots, and asked him for his thoughts. He replied,
"I cannot remember any great difficulties. The critical factors would have tended to be:-
1. Wing loading and span-loading towards the tip.
2. Wing tip chord and type of section.
3. Even an offset seat, when flown solo, did not cause significant trouble, because the wing loading was reduced - and with it the Reynolds number. Of course much could depend upon the Rn in theory, whether it is translated from turbulent to laminar, and the thickness ratio of the wing section near the tips....."
It's an interesting subject. Wish I could find our reports!