I also use a Heiland Splitgrade device and spent a few hours last Saturday with Jürgen Heiland during his visit to Monochrom Berlin discussing questions about the device. The Splitgrade system is a fantastic tool for getting good working prints very quickly. He would be the first to tell you that the exact settings for each paper are based on his own testing in his darkroom with his chemicals, his technique, his enlarger etc. That is to say if you find that prints with a particular paper/developer combination are generally too light, too dark, too hard or too soft for your own taste you should go ahead and find your correction (by test strips for example) and then enter the desired correction in the device (you can enter correction factors for your enlarger or for each paper). I don't think the problem is due to Ilford MGIV FB being flatter than the PE paper, I am pretty sure that the Dmax for Ilford MGIV FB is actually slightly higher (darker blacks) than for the PE paper. So don't give up on the Heiland Splitgrade and certainly don't give up on Ilford MGIV FB, it is a beautiful paper.