You might get a little more "depth" out of the preset by changing the Pitch knobs a few cents [Pitch A – A:0.999 / Pitch B – B:1.001]. It still has the problem of no direct control over the sweep rate. I tried different combinations of using the expression pedal as a manual LFO over the delay times themselves. But there's that little crossfade when sweeping delay times that disrupts the clean sweep (an advantage in most situations, though).
Care to post the settings?