I don't actually have any unperf on hand - trying to decide if I should buy a nice stash I saw for sale. So far I've only got some Aero Double-X and Rollei IR with the possibility of Aero Plus-X. I want to minimise modifications to the back of course.

As far as the Ilford ULF thing goes, you need to wait for the announcement mid-year and find a participating retailer, where you place a pre-order. The pre-orders are tallied and if there's enough demand for a particular size, the cutting happens in that size and you get the film a couple months later. It's mostly aimed at people wanting weird and/or large sizes like half-plate, 11x14 or whatever. I think in 2012 they ended up cutting both FP4 and HP5 to 70mm.