What is considered the safe range when hanging?

So I’ve been hanging for a couple years now and I’m starting to wonder if there is a sweet spot to get gains from, as well as a what is considered to much weight?

For me the sweet spot has always been around 11lbs to 15lbs, anything over 15 pounds and I start to get bruising and red spots that tend to get bigger the longer I stay at that weight.

I’ve been sticking to 12-15lbs and still gaining just going to different angles changing it up, shocking the body. It’s always over 15lbs is where I start to crop up vascular issues, no matter how well I wrap, even at a duration of 15min.