Couple thoughts - first off easiest would be hanging it off the 3pth of course just go look at how rear finishing mowers mount up so you can understand how they "float" when down on the ground.
The biggest problem you'll have with converting a mid mount deck are the deck wheels. A mid mount deck is not expected or designed to slew sideways very much given it's placement under the tractor. A rear mount (or front for that matter) will swing drastically left and right when turning the tractor. They have wheels designed to swing accordingly to accommodate this. Without seeing your midmount deck I don't know if it would work without changing.
Frankly though speaking from some one who uses a rear mount finishing mower I must say if I had a choice I'd prefer mowing with a mid mount. It's fine if you're just doing big open spaces but it's not so quick for anything else. Just my 2 cents worth on that. Personally I only went with the rear finisher as it was significantly cheaper given I could pick up a used unit that's not specific to my tractor.
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