If you want to re-try the RES mining then start with a Low RES (in the metallic ring, of course).
You will face mostly Eagles, Adders, and Sidewinders, and the cops should take care of everything for you.
The metals and yields will be better - meaning that you will get more concentrated fragments from the rocks that you find, which will yield higher percentages in your refinery bins.
Make sure you keep an eye on where the cops are so you can run to them if it gets too hot.
I mine RES regularly. If you want to wing up to mine co-op, shoot me an invite in-game.
Try 4A and move 20+ km from the res site.
I got loads of painite, platinum, etc. from there during last weeks CG
I've never tested it, but yeah you can stray pretty far. Even at 20km you'll still get RES yeilds, and
far less activity.