Go with the R1 tires and wheels. That way you can turn the wheels out to a wider postion to give you the stability you want and need. With the R4 tires and wheels you can't get as wide. I have R4's on my 3520 cab and no way could I ever get around my place with the R4 rear wheel stance. I ended up adding unverferth 4 inch extensions giving me another 8 inches width in the rear. It makes a difference but, I still can't take the 3520 in places I took my old JD870.
The cruise control is an easy install yourself. Just follow the instructions and you can do one is less than an hour.
I certainly don't want to start another tire war but I have R1's on my 790 and I get great traction on dirt and in snow. Wouldn't think of anything else. I actually thought the R4 would be more stable since they are lower and wider. Hadn't realized that the R1 wheels could be put wider. Thanks.