@BATTLEAXE has done this kind of flap on his BW (I think it was a BW) and he says it works really well.
The flaps i did on my original BW were integrated into the bottom plate like a split flap. And they did work well functionally with regards to how they worked and performed in the air. The cool part is they are hidden when not deployed
This an extra section added to the C fold on the back of the bottom plate to cover the opening of the flaps to the inside of the wing...
This way you can keep the aileron authority with full length control surfaces.