Geistware, if I were not finished with the wing, this would be my choice as well (and I'll probably do this on future planes just for grins anyway). I would have lengthened and split the aileron and installed more hinge points.

However, at this point I think I need to try something else as I don't believe there are enough hinges to safely split the aileron into two parts.

LATER:

I spent some more time looking at it and I would basically have to cut off the ailerons and make new ones. The current ailerons were built per plans and only have about 30 degrees max deflection, arguably not quite enough for flaps. I'm going for the gusto and installing 4" wide split flaps just ahead of the ailerons (this is really the best configuration I can do with the servo wire tube in place).