Eric on my Impact wing roots I applied a thin dense foam strip. I found these sheets of foam next to the felt at a Hobby Lobby, or other craft store. Just cut into strips and CAd it on. I also used soft balsa filler blocks to increase the bearing area of the wing root on the fuse in the area of the bolt and pins. This has prevented the marks you have on yours and the foam seems to have a high friction coefficient so the root doesnt slide around against the fuse.
Just another way to skin the cat.

Im enjoying flying this plane also. Have the same slight aileron trim issue but mostly leveled the ailerons using trim adjusters.

I have had some gear leg issues and have ordered a set of Bolly gear hoping they are more reliable.

Brian