Thanks, Cal for your input here and also in the 70mm thread. Getting a 70mm back for my Hassy was the idea that immediately came to mind. But of course I picked up a Linhof myself last year, and they were, indeed, very big on both 220 and 70mm. Mine is a 4 x 5" Super Technika, and I'm not sure all the same back options necessarily existed for the 2 x 3" and the LF Technikas (they have different backs and magazines, though I seem to recall there might have been certain converters from Linhof enabling one to be used on the other, possibly). I had a quick look last night, and they made 6 x 7 Cine Rollex 4 x 5" backs, for starters, and recent eBay sales suggest they don't cost very much either. It's certainly food for thought. I'll have to peruse my copy of Linhof Practice to see what other Cine Rollex magazines were available. The 645 type for the 2 x 3" is news to me, I wasn't previously aware of that one, so I think that's a pretty good score you've made there.
I'm often happy shooting Delta 100, Acros, FP4 Plus, Tmax 100 (when I can get it) and even Pan F Plus sometimes, so the true speed of the Rollei wouldn't faze me at all if the grain is fine, as it would seem to be for a "400" speed.
Cheers,
Brett