I just bought a bunch of boxes of this stuff in the 3.25" x 4" size, labeled "Kodak Electron Imaging Film SO-163," and tried my first test sheet today. It does, in fact, slide into a 4x5 holder in the 4" dimension just fine. Keeping it centered is another problem, though.

I rated it at EI 12 and developed it in HC-110 dil. B for five minutes in a rotary drum. The base of the tree was spot metered and placed on Zone III, but in the negative (and the scan) it looks more like Zone IV, so next time I will rate the film at EI 25. It could use a bit less development or a higher dilution to tame the contrast, and, being blue sensitive, the skies blew out completely. Close inspection of the scan shows almost zero visible grain. I have some old 3 1/4" x 4 1/4" film holders that I'm going to try using it with next.

For the record, the packaging states that the film can be handled under Wratten #1 or Kodak GBX-2 safelights (deep red).