I'm thinking about cutting a small horizontal groove in the wing tip from front to back, glueing a sheet of thin ply into the groove so that it sticks out maybe 3 inches, putting a couple of braces on the top and bottom, and then covering it with matching yellow packing tape. More or less is that how you did it?

Hehe, I guess the better question would be "how did you do yours" rather than me trying to reverse engineer it.