On Monday, May 18, 2015 at 5:38:43 PM UTC-4, PBA wrote:

I would be interested in protecting the base of the wing spar opening on the fuselage. Years of assemblies have started to wear a groove and it's getting thin. Something Teflon Based? I see from a previous post, not an easy material to bond to something else.

UHMWPE or the material from gap seals (and using GOOD double stick tape for either) makes a good "wear material" for the bottom of the spar box carry through. Something on the order of 0.040" is fine, biggest thing is to NOT go so thick that you remove the clearance between the box & the spar bottom..
Of course, lifting the wing all the way in is free, some sort of protection is worth it.