Hello I'm Chris

To answer this question it all depends on the trailer your using. There is not a posted spec for the question your asking. So you will need to actually jack up the front of the RV to see how high you can get it prior to the section beyond the trailer wheels getting to close to the ground. You also need to know factor in how un level the RV will be during transit resulting in many items ending up in the back of the RV after a trip and any fluid holding tanks possibly spilling over from constant fluid pressure on there back flow valves. Another concern is the tandem axles not weight centered and bottoming out on bumps. Another problem may be the jacks o n the trailer not able to go this high.

For the average road you need 8-10 inches between the bed and RV body underside to prevent impacts on some inclines and declines. A 5th wheel hookup can be modified slightly and still be structurally sound to allow for this height difference.