It seems to me that if:
1) Your suspension is compressed 4-8 inches with the weight of the camper, and;
2) The amount of leveling needed is less than that, then,
3) If you leave the turn buckles on you should be able to level with out an issue.
I do this on a regular basis. I am simply taking some tension off the suspension the same as if I undid the buckles. There is no difference in bed to camper distance. Obviously if I need more than I unhook but this was a lot simpler and quicker with electric jacks than it was carrying around blocks of 2X12.