Sorry it took me to reply, i havnt checked this thread in a while. you already probably have it done but il tell you how im doing the inner leading edge.

i measured 18cm out from the edge of the wing. i cut a wedge shaped slot there. i shaped the balsa block to fit in between the wing and extra rib.
I did that just there so il post again when i have it sanded smooth. im probably gonna just glue the veneer straight to the wing.