I also have 22 inches for my single tank setup. I prefer regular rubber hose than miflex type. As for bungee, don't need to order online. Just go to West Marine type of shop, they have them. Just buy a couple of feet, rig it up, test it, then cut the extra off.
Before putting backup on necklace, make sure you primary is the donatable reg. That means probably longer than convential LP hose. Most people use 5ft or 7ft.
DGX website has a step by step instruction showing how to tight snap to hose. The key for easy clip thing onto d-ring is the placement of the d ring. BAUE.ORG has guideline for that.