I didn't realize you had a Hasselblad. I think you may find it easier with a leaf shutter that can sync at any speed etc than with the F3.

Probably what I would try is if you don't have one, rent a polaroid back. It will probably save in the long run because you have pretty instant results and can adjust right away instead of going back repeatedly with the 35mm.

You can also easily mark the ground glass, for where the model is and moved to if doing multiple flashes.

Good luck

PS.. I trained JKD with Danny Inosanto in LA for a few years.