I had a couple of MK Arrows with flap /spoilers. they had slots in the wings under the spoilers. Can't remember whether I added them or they were on the
<font color="#000000">plans</font>. Worrked great however. I scratched a couple of Dirty Birdy's with them too. Worked great there too. I remember having a very short field and they made landing these speed demons easy.
Do you mean a recessed area in the dorsal aspect of the wing in front of the flap, or are you talking about a slot for a ladder-style spoiler? I'd like to see a pic in any case if you have one handy.