I have never done dual tires on a Gator but I have on a ATV. I sometimes hunt in swamps and the extra floatation was very noticeable and a big help. The problem is the front. Adding duals really makes steering an arm workout. Then there is the concern about the overhung load so you have to be careful how you drive unless you don't mind breaking things. As a later/final configuration I have larger diameter tires on the vehicle and my "extra" outboard wheels are smaller diameter. On level ground the outer wheels didn't touch the ground much so most of the time steering was OK but it can be very erratic if the outer wheel suddenly makes contact with something when you aren't expecting it.
For a Gator I would do the rear wheels only. I would install a narrower tire like used on the front to minimize the overhung load and limit the width of the vehicle.
I have a hard working Gator 855D on the farm and some of my ground is seasonally very wet. The Gator is a great machine and I really don't know what I would do without it, but, ground clearance has always been an issue, and it is vastly under-tyred from the factory for what I need. It is now 4...
You don't need dual wheels. You just need to widen your wheelbase. Simple spacers can move your wheels further out for better stability without the downsides of dual wheels.
My ATV was used in swamps where the ground is extremally soft which helps keep the overhung load manageable. In your case catching an outer wheel on the steep road edge while heavily loaded is an easy way to break something. But if you are interested here are some cheap & easy spacers I made for installing the extra set of wheels.