I won't say this is wrong. However... Many a kit emphasize this is not necessary at all. Personally, I have always found myself doing just as cfircav8r suggests here.

On my first miniplane I used 3/32 inch ply. The other two mini's used 1/16" balsa. The grain is vertical. One side (either side of the spar) is sufficient. My shear webbing was glued on the aft of the spar.

Another option in place of the shear webbing is the truss system with 1/4" balsa sticks. It is 6 one way, a half dozen the other. Whatever floats your boat.

Lookin' good!

Brian