Yes, just the warp amount, Jon. It's way overdone in those small tests but the warp amount really only needs a small range over the entire animation to be nice, especially if, like I said above, you let the lead-in scale just pull the features around, the feature scales react very convincingly to the large warp stretching with 'less warp at feature scale' enabled.
Don't overdo it, though! I've used a range of only '0.4' difference over 750 frames for 30 seconds of footage, and I think that might be too much. Post later on, frame 272 now...