Two simple solution options from me.
Top Picture Stainless ring (or D-Ring) connected to dSMB with SS screwgate
Second Pic, Stainless ring (or D-Ring) simply had dSMB webbing threaded through it
All my spools have a spring gate which attaches to the dSMB ring (You could permanently attach yours if you like). The bungee cord on the spring gate goes around the spool and stops it unwinding if the double ender comes off or if I fumble it getting it out of pocket
My dSMB and spool stay connected during dive (dSMB goes in a pocket, spool normally hangs outside clipped with double ender for additional security (and I use double ender to clip off line to spool at a stop)
I have a (large) number of spools of varying sizes, as well as 4 or 5 different dSMB's hence I prefer the ability to quickly re rig depending on usage, or even detach spool during the dive if I need a line for anything. Personal pref
Top Picture Stainless ring (or D-Ring) connected to dSMB with SS screwgate
Second Pic, Stainless ring (or D-Ring) simply had dSMB webbing threaded through it
All my spools have a spring gate which attaches to the dSMB ring (You could permanently attach yours if you like). The bungee cord on the spring gate goes around the spool and stops it unwinding if the double ender comes off or if I fumble it getting it out of pocket
My dSMB and spool stay connected during dive (dSMB goes in a pocket, spool normally hangs outside clipped with double ender for additional security (and I use double ender to clip off line to spool at a stop)
I have a (large) number of spools of varying sizes, as well as 4 or 5 different dSMB's hence I prefer the ability to quickly re rig depending on usage, or even detach spool during the dive if I need a line for anything. Personal pref