Looks great so far!
Regarding the upperwing strut fit, you could put some tape on the wing, fit in place and build up the strut attachment area, then remove the wing, and the tape should keep the putty from sticking to it (if that makes sense). Otherwise, you could carve out an indentation the same shape as the strut end so it is a little recessed into the upper wing. Sorry, that is about the best I can think of.