This is a parachute line retainer i designed. It works for any parachutes with 10 lines or less (if they're symmetrical). my nylon disk gap band parachute I made performed flawlessly with the retainer! It used to twist all the time. A swivel helps a lot, but pair the retainer with the swivel, and it works phenomenally based on my experience. I hope this helps you too, and if you have any suggestions or request (like your parachute has more than 10 lines) feel free to comment!
After printing and connecting lines, zip-tie around the retainer to keep the lines in better.