Normally my leg loops hang down close to the widest section of my thighs. When hanging in the harness, that puts in the leg strap under the middle of the hamstring and is very comfortable for up to a minute.
But hanging with the leg strap under the hamstring for more than a minute sometimes creates a sensation of not getting enough blood to the lower leg. I found moving the leg loop back (to somewhere between the hamstring and the butt) allows me to hang for several minutes without that problem. (It creates another form of discomfort, though, so not good for short-term hangs). Maybe useful if you ever find yourself hanging longer than planned.
I find harness leg loops incredibly uncomfortable if they're not between my hamstring and my butt, you know you have the position right when it makes you look like a male stripper packing an anaconda in your pants.