I installed one inside and found it very hard to do and use. Found all the heat from the engine and turbo cooler was to much for winch. Installed Polaris winch bumper and moved it outside. Much easier to install/use. Bumper is a great and very easy install.
Check out the KFI winch mount. I just ordered that along with 6000 pound wide spool Viper winch from proutvparts.com. Less money and more power than Polaris. The nice thing about the wide spool is 65 feet of cable versus 40.
I installed the winch over the front diff. It's snug but goes in without issues. Take the mounting plate off the RZR first, attach it to the winch and install it all at once. Much easier IMO. With an extra set of hands, it will slide into place.
It seems to me that it was designed to have one mounted there, but after it was produced they went "oops" that's a tight fit and created the aftermarket Polaris mount. It is sweet that you got one to fit in there. I opted for the mount in case there were issues with the winch to make it easier for maintenance.
l believe your success of getting a winch mounted over the front differential has a lot to do with the size and manufacture of the winch.
l tried to mount a 4500 Viper Elite and failed miserably. When l say miserably, l really mean it! I removed mounting plate and bolted to winch first, disconnected spring and shock assembly arm, and tied it and numerous hoses up out of the way. I then pushed, pulled, and pried it into place, only to find out the mounting plate holes would not line up because of the winch was up against the shroud around the radiator.🤬
A smaller or different winch could work, as others have stated, but it wasn’t worth it to me. The outtie is much more accessible, and there are no concerns about heat build-up.
I have a Viper Elite 4500 installed above the differential. It is a tight fit but it does fit. It has to go in with the winch motor pointing towards the passenger side of the vehicle. I had to slightly file the radiator mount because the selector knob of the winch was touching it. I also had to re-clock the motor on the winch to keep one of the winch power wires from rubbing a coolant line. These were very minor modifications to get the winch to fit. It has worked flawlessly for me.
I know you asked about mounting over the differential & thought I`d throw in my 2 cents.
I really wanted to mount mine over the diff because I thought mounting external wouldn`t look right. In the end I went with the SuperAtv mount and winch and it was a very easy install and the look isn't bad at all. I ordered their mount for a factory bumper then used the holes intended for the bumper for a low profile light bar. I've been very happy with it and glad I didn`t do it the hard way for a change!