Hello and good evening Mike,
In any case you want and need a mule with loaded tires when dealing with slopes
as it adds to the machines stability with or without an implement.
You can if you want to do it that way sure, you only have to raise it a few inches but as fallon says its better to leave it on the ground and the rear roller will not mind.
The rule of thumb to follow is; do not back up the slope if you can slide on the sod with a boot and the heel holds moisture especially if you have turf tires. Better to have have loaded R2 tires(Ag lug tires) as you need more traction.
If you travel at 2 miles an hour up hill you are moving at 3 feet per second rounded so you can travel down hill at 2 miles an hour and have a very fine mowing with a brush mowing flail.
Just do not try to mow fast as you need to be sure to wear your seat belt and have the rops up and locked and the brake pedals locked together to avoid slipping across a pedal and locking one wheel.