usage

My guess is that it would kind of work. When you put it on and tighten it down the G-string strap would press against a plug base and help hold it in, but there wouldn't be anything "grabbing" the plug so you might need to adjust things from time to time to keep everything in position.

Keep in mind that it would probably be a bit uncomfortable for someone with a penis to use as a plug harness .

Unless you stay still, the harness wouldn't work well as a butt plug harness. You really need a ring or something to make it stable if you're looking to move.