I've been using ABC plus for about 8 years now, normally with Efke or Foma Film. I processed some FP4 the other day and was surprised by the flat negatives I viewed. Exposure was bang on, temp and time. I also processed a couple of Efke in the same drum, no problems there. I thought that maybe a silver rich film may stain more so than a mass produced film? Pre wash 5min Kodalk. Dev. Wash x 2. Fix 250grms Sodium thiosulfate + 10 grams Kodalk. After wash 2 min Kodalk. Then 10 x 2 minute washes in the drum. Can't remember the dev time, I think 7.5 minutes. Look at the range of the two films and found the FP4 flat. I used the blue channel on the spectrometer. Any feedback?
Sorry this took so long to get to, but IME, Ilford HP and FP films require longer developing times in pyro to achieve decent contrast. I don't use the same dev as you, but in Pyrocat-HD and PMK Pyro I need extra time over even Pan F+ to get the CI I am looking for. Yo also have to bear in mind that just looking at or scanning won't tell oyu much, you need to print them to get a true evaluation. PC-HD negs usually look thin to me, but print beautifully.