Dude that is awesome! Nice sling as well. Instead of knotting the leather thong, I lashed mine with wax coated cord. It works better and looks awesome.
I’m sure you know this, but the studs will only work with a thonged sling. They will not work properly with sling swivels.
Google Winchester or Parker hale fish hook swivels. Expect to pay $80-$150 a pair. It’s 100% what that was intended to use. I use English swivel eyes on restorations for fish hook use.Actually the holes on mine are much larger than standard studs. Would this match the fish hook swivels you mention? I’m not familiar with them.