Update.
So, knowing how the Rolleiflex back is supposed to work, and knowing that the glass doesn't touch the film plane of the Instant Film, it is probably unreasonable to expect a sharp image at anything except stopped down.
So, to make this happen a lot of things need to come together.
1) A working SL2000f or SL3003.
I have 4 and 2 still work!
2) Batteries for the above.
See my related post on batteries; I just upgraded the batteries in my SL3003 battery packs to low self-discharge nickel–metal hydride batteries. I already made a charging adapter.
3) Powerful flash to allow one to shoot at F11 or F16 with the ISO 100 instant film (of course the ISO 3000 film is gone).
See my related post on batteries for the powerful Rollei E36 Flash. Now powered by a 3-cell LiPo.
4) Film
Perhaps not available for long, but as of today I can still order more Fuji FP-100C.
I have been fiddling with this SL2000 Polaroid back since 2003 but never got it to work well.
Today I finally got some very nice, but very tiny, images. Like many things in art, I'm re-purposing what was once a professional proofing device (the Polaroid back) for the fun of just making tiny instant pictures for friends and family.