Seriously, you guys tend to overcomplicate this stuff.
Subq is subq where ever you have fat to shoot into. If you have fat on your ankles you can shoot there, though I'd suggest diet changes before peptides in that case.
The welts come either from a very slight infection (similar to when you get a small cut and don't clean it properly) or from pockets of water getting "stuck" in the fat. Not sure if this is exactly what is going on with the latter, but I've certainly experienced something similar, which caused me to think about the issue, as I didn't want ripped, leprous abs. I moved back to the glutes, exact same site for IM injections, problem solved.