RE: Extra 260 75cc
There should be no vacuum, as the wing sockets are not sealed. You will find that after inserting and removing the tube after 3-5 days of flying, it will get easier. The wing allignment dowels are probably your biggest source of difficulty. Again, this is actually a good thing to have a tight fit, and it will get easier with time. However, you may want to take a look at the holes in the fuse for the tubes and sockets and make sure there's no melted ultracote in them - maybe clean them up with an xacto - just make sure you are not enlarging them. These are laser-cut, jig-built planes, so the holes weren't cut to small.
I had the same difficulty as you, but I cleaned up the holes and just dealt with it for the first five flights and it was fine after that.