I would certainly expect the rental house to provide you with the necessary, up-to-date software to support their cameras.
In addition, any Hasselblad dealer should be happy to provide you with up-to-date versions of FlexColor, to allow proper configuration of this recent release of Phocus. This is certainly something I have available for customers at any given moment (via Apple iDisk, support web links, USB thumb-drives, Factory CD's, etc).
You can expect an appreciable speed improvement with Phocus, over FlexColor. This is accomplished on several levels, most importantly by its more elegant support, and inter-operation, of both .fff and .3fr files.
If you would like an up-to-date copy of FlexColor, feel free to contact me directly.
Bummer I only rent a Hasseblad when needed and haven't yet got around to installing Flexcolour on my new Mac. Not owning a Blad means I can't log in to download Flexcolour for the Mac!
Annoying as I have some images from last year I haven't had time to process and I hoped Phocus would be somewhat quicker then the awful Flexcolour to use. I had a play with it at Focus and it seemed pretty decent if a little rough round edges, but it is a Beta..