This!I agree that you can set up a sidemount rig without hoses around the neck. Hose routing around the neck is a function of Hogarthian backmounting that has carried over to sidemounting. I don't like swivels (especially those pictured in post #5) due to their tendency to fail,but prefer a 90 degree adapter on my left tank.
No swivels, only elbows. I've tried 70 (also called 110), and 90; much prefer the 90.
I like it so much I've switched my single-tank recreational over to the alternate being on a necklace, and the primary coming under my right arm with a 90 deg elbow on a longer hose.