elgoog:
There is absolutely no reason to add a second hip D-Ring. As others have recommended learn to clip the stage bolt snap. Be mindful that all of the tech training courses, whether GUE, TDI, etc will give you a start and a beginning. None of us are experts after finishing courses. With practice, what came with difficulty will come with ease. Yes, reattaching your SPG to your hip D-ring will pose a challenge when there is a second bolt snap, and possibly a third depending on what you brought with you on the dive.
Take your time with the procedure. Logically think and reason out the problem. Have I gone gate to gate, gate to body of bolt snap? Have I foobared the restowing of the stage reg? Many times!! Cool thing is my buddy is in front and we debrief after the dive to discuss the hickups and what we need to do for improvements...
R3 teaches deco with 32%, hence you won't have to relabel your cylinder, whether you use it as a deco or stage bottle. However, as your instructor has undoubtedly told you, the stage is used before your backgas. Some of us started carrying stage bottles strictly for the practice of deployent/restowing of hoses and to learn to reclip on the hip D-Ring, regardless of the required gas expenditure. I will caution you with a certain mentality that developed with this, the gradual development of laziness in analyzing the required amount of gas for a specific dive plan and just brining extra gas... Yes, I had to unwean myself from this...
O.