For FP4 I've been using Ilford Universal PQ developer in a Jobo drum on a motor base, for both pt/pd and for carbon printing. I have been using it 40:960 to 60:940 at 62 to 68F for 4 to 10 minutes -- depending on the contrast range of the scene and the process I am aiming for. For Carbon printing I am aiming for highlights just shy of blocking up.
Just about at the end of my supply. Sorry, no idea what my density range is, but I usually print without any contrast agent for pt/pd. And if I have pushed things too far and the neg is too contrasty for pt/pd, then I know it will make a great neg for carbon printing.
I've used HC-110b with TMax100 with good results also -- pushing the development times towards 20+ minutes (constant agitation, 68F) to get very high contrast negs for Carbon Printing...negs won't print with pt/pd, but might with the self-masking of Zias.
Vaughn