Thanks for all the replies. FYI, the question was prompted by the construction of my first kit - a CG Tiger 60. The wing tips are to be carved from triangle stock and I was looking for input on how different shape tips would effect the plane.
I have decided to take the lazy way out and extend the airfoil on top and smooth the existing 45* angle on the bottom of the wing tip. This leaves about the last 20% of the tip with a rounded curve from top to bottom while the rest is a 45* angle to the top of the wing.

Bill wheeler