RV fridges should be level when parked because sodium chromate, added to the coolant, will crystallize and block the tubes, but only while the fridge is operating. This situation is not reversible.
When driving, normal bouncing keeps things moving--or, if weather and distance permit, don't run the fridge at all while driving.
There is a line somewhere in the owner's manual that a fridge is ok if you can walk around inside the camper without noticing an out of level situation. I don't obsess over being level and just use a short, but good quality, torpedo level on the floor just inside the door. The 2499 also has a swinging bathroom door that is a dead giveaway about an out of level situation. I use the level more to help decide which side stabilizers to put down first--the low side.
Cabinetry is not always level and I suppose a floor may not be either, so where you measure depends on how much difference you might notice by taking a couple of shots. As I said above, in practice I really don't think it will matter as long as the trailer "looks and feels level."