A P-500 with OEM roof will be to tall to fit, which is why I went with the EMP roof which only adds 1/2" to 5/8" above ROPS.
I'm running 26" Blackwater Evo tires and have since added Elka Stage 1 shocks and the unit sits at 71-7/8" with no problem loading into my enclosed trailer with about a 72" vertical clearance so you should be good.
Also remember that as the front wheels are in the trailer, the rear wheels are still on the ramp the highest point of the roof or ROPS is already inside the door so as the rear wheels clear the ramp, the P-500 is already inside. I actually think I could go up to 27" Evo's and still clear the door.
As additional food for thought, you can also lower air pressure to gain more clearance.