That wing is probably one of the easiest types I've ever had to scratch build. all of the ribs are the same and can be "bulk" sanded, notched and holed. LE and TE are standard stock and wing tips are easily cut as well from 1/8 balsa stock. If you need a set of plans and/or some rib outlines PM me.

Or just get another whole kit...keep the second fuselage for yourself...with a set of floats up under it! Once you put it one the water you'll enjoy a whole new cub experience.