Lift bags stow very easily when passed through two bungee loops passed through the bottom of the plate. They are streamlined and not prone to get entangled in that location and it involves minimal hardware - all very "hog". An open circuit or semi closed circuit SMB can be stored the same way - just fold it to the same lenght as the bottom of the back plate, roll it up and slide it through the bungee loops.
Closed circuit SMB's are not ammenable to that method as the rigid inflators are almost invaraiably positioned across the width of the SMB to promote rolling lenghtwise, which eliminates folding the rolling the bag widthwise as an option. That means they end up in a pocket.
I regard having a closed curcuit SMB dangle off a D-ring as the absolute last resort due to the line trapping, unrolling and general confusion with SPG, stages, etc that can occur. If a hip pocket is not available, then I would consider a pouch attached to the back plate on the side opposite where you'd place an argon bottle. You see technical divers clipping all manner of crap to d-rings, but that does not make it right. If it potentially interferes with easy access to something else on the D-ring, or increases the potential for line trapping, don't put it there. Adding d-rings to the base of stages etc, is just making things worse in terms of tangles and dangles.
If a hip pocket or a pouch on the BP is not an option, put the closed circuit SMB on a butt D-ring but don't put a spool there - a reel yes, a spool no - for the reasons mentioned in previous posts.
I saw something on the boat yesterday that would work great for an SMB and line attached there if the proposed use is as a Jersey upline. Visualize a 6" to 8" piece of 1/2" diameter PVC with flat plates cut from PVC drain plugs on each end held together with a SS eye bolt. Cut the 1/2" tube to the lenght required to roll your SMB between the end plates, add the lenght of line required, attach the SMB and roll the bag on top. Then turn the end plates down to the diameter needed to be flush or just slightly above the SMB then re-assemble and secure the SMB in place on top with a strip of inner tube, etc.
The end result is a mini Jersey upline not much larger in diameter than your rolled SMB, but it is contained in a compact package that you can clip to your butt D-ring with either a double ender or a bolt snap installed inside the eye bolt with no entanglement worries. The bag is sent up just like you would with a cold water spool.
How you use the SMB depends on the conditions where you dive and that impacts how you carry it. Personally in the great lakes or along the mid atlantic coast, I'd shoot a 100 lb lift bag for normal deco purposes and shoot a closed circuit SMB when things go bad and I need to be seen. If I am in a current and I am ascending off the anchor line, I shoot an upline attached to the wreck so that I stay on the numbers in locations where fog or sea state coudl make tracking a drifting diver difficult. If I am on the surface and drifting away from the boat, I'll deploy a closed circuit SMB to get the extra height and visibility. That means on the average dive the CC SMB stay in the hip pocket with the other "here I am" stuff and is not used at all, unless as a jersey upline or on the surface.
If you dive someplace where drifing deco is the norm, your mileage will vary, but where ever you dive, adjust your configuration to optimize it to the conditions YOU will encounter not the conditions some other internet diver may encounter whereever he or she dives.