I have made the experience that one should not tighten the Gitzo G-locks too much. You will ruin them that way with time. I donīt know about the older models but with the new G-locks, the legs are locked properly even if they are tighten gently with just two fingers. I think a 3 series Gitzo will be best for a Hasselblad though a 2 series will suffice. I used a 2 Series CF even with SL66 and 250mm Sonnar and it worked. Concerning the head: do you want a ball head or 3-way?