I just tried Gainer's trick of adding fixer concentrate to the developer after the completion of development, and I like it.
I was just testing a new filmholder and just had to do one 4x5" sheet of Efke PL100, and I've been wondering what to do with an excess of Zonal Pro rapid fixer that I have on hand since switching to TF-4, and this is it. I developed the film in a tray in 300 ml of PMK and added 50 ml of fixer concentrate and fixed for 2 min. This was too much fixer and reduced the stain slightly from what I usually expect with PL100 in PMK, but the neg is still pretty good with no obvious pinholes, and I'd definitely do it again, but with less fixer concentrate. It was quick and easy, and I could develop, fix, and wash in one tray.
Comparing the use of Polaroid type 55 with the need to coat prints and clear and rinse negs anyway, it's not much more difficult to use this method for similar applications (i.e., test shots and situations where I'm not worried about archival stability).