Starkeeper, you should be able to save the DSP settings in registration memory. Works on the 740. As to rotary setting I just pick whatever sounds good. I tend to use vibrato instead though as it sounds a bit more Hammond like for some reason. Unfortunately you can't get at it from the keyboard - you have to use sysex. One of the sysex editors will do it - XGEdit, XGPad, XGGold or XGWorks. Or you can cobble your own and use Cakewalk or whatever.

Bryan