Isn't this primarily a sidemount wing with some capability for back mount singles?
yes the sms 100 bcd is an SM rig, but it's not great for back mount, I've heard the weight can deform the soft backplate, but I think @loosenit2 is referring to just the wing alone.
I do already have one (although attached to my SM rig) and hadn't thought of re-using it, is it easy to mount the bladder as a wing to a BP?