My composite wing tips are a bit narrower than the wing, so I cut some wooden sticks and used them to test fit the tips until I got the right width that provided a nice, snug fit with the wing skins.
What worked for me a was resulting width of 6.5" and 17.5" from the leading edge. I later checked this with the NACA 4415 airfoil (Sling 2 airfoil from what I have read) and its pretty close.
