Are you using the yellow hollow poly rope? That's what I use for my hoop nets, I've been using it for years and have never had it slip where I braid it to make the loop(s). Most of my hooping is done in depth of 40' or less or anything deeper than 75'. If I'm in 40' or less its one line but if I'm in crab waters (typically 75' - 100'+) I will loop another piece or two. I've tried using the 100' pieces in the shallower waters but its to much work trying to keep the excess line tied together, I like to keep it simple. Additionally, because the line is braided into a loop it allows the two pieces that I looped together to go through my Trapeze without getting hung up by a knot.I'm sure there are others way to do it but for me this is the easiest way.
Here are some before and after pics