having bought 3 Great Planes Super Skybolts, all within 3 months, i can tell you there are huge variables in the covering jobs............ "traveling around the globe" has nothing to do with how it was apllied in the first place. i also don't believe in the ever growing airframe excuse either.

i come from the Free Flight competition scene, and we never had to touch our wings and stabs after being covered.........most planes survive 3-4 years.

of all 3 kits, i could honestly make up 1 kit that had what i would call a workable covering job.
the 2 little Reactor jobs i bought whe those came out were perfect.
the 2 Super Stearmans i bought were above average.

you've done a great job getting most of the sagging out, but for me, it's not good enough.

to be fair to GP though, they (actually Hobbico) replaced 1 stab, 1 fusealage, and 2 wing sets along with several cowls as all the kit cowls had cracks from the Mfg. packing the metal hardware inside the cowls for shipping.

with the pictures you displayed, i will go out on a limb here and say they will probably send you a new wing.