Jim, I made the F3 the same as F2 Just the top half. and F 4 just about 1/4" taller than F5, it gives you a straight line to mount the headrest on.
I have a 19.8 cc Kerowitz gas motor I am going to try. I need to find an electronic ignition for it so I can get rid of all that bulk on the front. I'm thinking about making a fiberglass cowl for it.
I also am planning on using gear in front of the wings.
I think I will use 6 deg dihedral, I think the plans call for 12. Is that right?
I might post some pics later tonight.