Can you hang your SPG from your chest D-ring? Sure - and many responses indicate that others do as well. You describe your rig as mostly DIR. Are you interested in DIR? If so, I invite you to take a DIR class and learn the cons first hand - and then decide for yourself. DIR isn't just a piece of gear or a place to hang your SPG - it is a complete diving philosophy of gear, procedures, and attitude. Changing one thing throws the whole completeness of the system off. It's about starting with a base system of gear, procedures, and team, and building on it - from the beginning level all the way through tec / cave 2 etc. For example, in DIR there is no such thing as a Rec system and a Tec system. Take a class, and learn the complete philosophy - then the answer to your question will make more sense than a one sentence answer on Scubaboard. Cheers