Hi Ben;

With plates extending below the wing, the increase in lift at ground-effect level would lower the stall speed at flare-out, which is what I observed with the adjustable plates on my "stick" back in the 1980's.

Other than that, I wouldn't expect any change in the stall characteristics, since that is something that occurs on the top side of the wing.

If this image isn't too large to attach, check the tipplets on this gargantuan Russian surface-effect mobile missile launcher. Maximum altitude: 10 meters. Speed? Fast. See, we're not the only ones who build fantastic weapons systems that are never deployed.