I really did not like the feel on our terrain, felt very tippy...so I put on some BORA 2.5 spacers and filled the back tires. That made a big difference, but still felt tippy on some areas....so I switched the 2.5 inch spacers for some 5 inch ones...and WOW, feels like a different machine, the added 5 inches (going from the 2.5 to the 5) seems like the sweet spot, I don't feel tippy at all anymore. Works great for my purposes now. Can't speak on how the R4 tires feel, but for hills, I think the R1s provide better traction anyway......
Even without the spacers, the tractor goes up and down hills with no problem, no traction issues and the gears hold it up or down. Going across was causing the butt factor....