Here's a couple of things I found trying make our RZR 4 fit and keeping the lower bunk in our Raptor.
The stop switch at the top for the bunks had 2 different mounting holes and was in the lower hole from the factory, moved it to the top and it allowed both bunks to go an inch higher. Also the lower bunk had different mount holes for the brackets on the trollies so was able to move to the top holes and gained another 1 1/2". So gained 2 1/2" by making those adjustments, then as others have said lowered the air pressure in the rear tires and dropped the back of the RZR about another 1 1/2".
( the rear of the cage is the tallest part so you only need to lower the rear tires)
Also I'm not familiar with your trailer but if the rear of the garage is dove-tailed the rear tires will ride there and drop the rear cage height down another couple of inches.
BTW, don't know if you looked at the RZR 4 800 but the height is 75" as opposed to the Honda 4 at 78" and the Kawasaki 4 seater at 79".