You'll have to forgive me for not being fully up to speed with bicycle parts, but, the dropouts are the little "hooks" that the wheels slide onto, before the bolts are tightened, correct?
Unfortunately, those are not removable, they are built into the frame itself. I'll likely try the "package tray" first, and take some photos of it in case it does go wrong. That part is so rusty, I really haven't much to lose. The issue I have run into, is the fact that I have to lightly sand the metal with #0000 steel wool to remove the rust from the surface. The vinegar "loosens" it, but it doesn't dissolve it. That simple act of gently polishing/buffing/sanding/etc. us what I'm worried about, as far as it wiping the paint with the rust, if the vinegar doesn't dissolve it.