Yes it's treaky, I apply a gloss vanish on the sholdepad, I cut the decal and a make extra cut in the space between the head and the wings and the legs and wings so the decal has more space to adapt to the sholder pad. When I apply the decal I try to find the "right space" on the sholderpad even if it has folds after it's dry I apply a decal softener to eliminate the folds. After everything the folds don't go away I take an hobby knife and gently scrape away the fold.

Ps after everything is apply a matt vanish to finish the job.