FP4 responded well to 'Nucleol BF200' a developer of Italian manufacture. I don't know if BF200 is still in production, but it's certainly not easy to find in the UK. I haven't yet tried it with FP4plus.(posted 8428 days ago)
I used to use PanF a lot, until Tmax100 came out. In terms of pure fineness of grain there's no contest; Tmax blows PanF away, but still seems to be slightly less sharp. I prefer the tonality of Tmax though, and stopped using PanF many years ago.
The sharpest negatives I've ever obtained were on FP4.