With a tractor you can place the hitch anywhere you want it. Location does not matter with the small amount of weight RVers haul. If you want it behind the axle that's no problem.
If you plan to build a bed on the frame, the current wheelbase, and how long a WB you want to wind up with, can be determining factors on which axle to remove if you remove either one, and how much of the frame rail ends, if any, you will cut off.
IM curions as to what State you are in, and how you registered your Volvo with a 42 inch sleeper.