I use the adapter with mine and it works by becoming the part that attaches to the light stand so it takes the weight rather than the head. It's all thick metal and has a locking collar. I've successfully used an octa softbox on it without any problems. There is a small mod you can make to the adapter to use some locking washers instead of the standard smooth ones. I think I read somewhere that the serated locking washers were now standard on the adapter.
Google for elinchrom quadra adapter mod and you'll find pictures and directions for the mod.
I use the Quadra along with the Eco Ringflash, and normal Elinchrom modifiers (I've used the 53" Octa on the adaptor with no problem). Great lightweight bit of kit and the ring flash is a cheap way of achieving on axis fill and the ring flash look. The ability to change the power through the trigger is useful when playing hide and seek with the sun outside.
One thing to note unlike the Ranger it's not waterproof so it's probably best to keep it in or near a bag if using it outside.