I'm vexed by this problem, too. The Arca-Swiss-type QR system has become a world standard, and furthermore, the bottoms of the Hasselblad Quick Release/Coupling clamps do not have the type of fittings that robustly connect to, say, a RRS ballhead shaft, just a 3/8 and 1/4" threaded socket with no torque control. I can see three solutions as it stands, should you not want to add bulk to the underside of your camera or switch all your industry-standard equipment to the proprietary Hasselblad system:
1. Replace the foot on your Hasselblad with the ClearSight foot ($60).
2. Replace the foot on your Hasselblad with the Markins P60H foot (should be $55, but not really in production for some reason. Found on eBay for $130)
3. Keep your Hasselblad foot and buy a Hasselblad Quick Release clamp and fit it to any generic Arca-style plate. This way, you can keep all your other camera systems on Arca, then attach the easily-removable Hasselblad QR clamp to any of your existing Arca/RRS/Markins/Kirk ballheads when you're shooting with your Hasselblad. It's two more layers of metal, but at least it's on your tripod and not stuck to the underside of your camera. A kludge to be sure, but maybe the path of least resistance?
