I noticed the same with HP5+ -- but I was always going to give it a try in D-19, and perhaps a staining developer might make it more useful for alt processes.
X-ray film is cheap and definitely can build up contrast. Takes careful handling (emulsion on both sides). The Agfa film I have seems to be about 400 ISO under the big blue sky, but seems to drop some when under the trees. I am not 100% sold on the stuff yet. I just happen to have about 300 sheets of it (14x17). I have been using it in a 7x17, and have done a few in 8x10.
Its slower, but I like FP4+ for both pt/pd and carbon.
Alas, Kodak Copy Film was a pleasure to use -- talk about building up density! I shot a box of Ilford copy film...nice also, but not quite the same thing.
Vaughn