ORIGINAL: K-Bob
I had to mount a sanding pad on a steel shaft and run it up and down the wing tubes for quite a while but now the wings slide on and off pretty good. They wouldn't go all the way in without considerable force before that.
The wing tube carrier sleeves will compress over time and increase in (internal) diameter under the vibration so I never sand the sleeves. Rather I powder it well with cornstarch or baby powder to cut the friction. Usually this is enough to allow the tube to slide into the wing sockets before the first dozen or so flights.
Good luck with the first flight! A friend of mind used to fly this plane (in the Red Bull scheme) in airshows, with smoke and everything. It was outstanding! He felt very comfortable landing on our tiny 75'x350', tree- and boulder-surrounded, grass strip. The plane would just float in for landing nicely.