This is interesting. The very biggest Class C's built on cutaway van chassis are on Ford E450. Some of us have smaller C's on E450 but most of those that ARE on Ford use E350 with a ton or so less rear axle capacity than E450. But if it's a small C on Chevy it'll be a 4500. That extra capacity's going to show up somewhere - ride stiffness and/or height. My guess is that the rear springs will settle a little and the difference will decrease.
What's your wheelbase? If it's around 159" the placement of the front HWH jacks will be far enough toward the rear axle that a lot of the lift you want in front is also shared with the rear. Measure front and rear reference heights before you level. If the front is lifted, I think you'll find the rear is lifted a couple inches too. This is a characteristic of C's with jacks, magnified in the shorter ones.