That one picture above showing the empty bucket, I was actually kinda stuck, I probably could have backed up, but didn't want to ... I had forgotten to add rocks to the bucket before mowing, as the brush hog is a tad heavy, and it's hard to steer without extra weight up front, in 4X4 mode, the front tires wouldn't keep me going straight on that bank, or turn me back up the hill ...
So I dropped the bucket and very carefully got off on the up hill side, as my own seat of the pants "Tip-O-Meter" was going off!
I gingerly let go of the ROPS and it was steady ... I gave it a light nudge, still rock steady ... The a push ... Finally I pushed it as hard as I could on the ROPS above the rifle, still couldn't budge it!
I then went down in the creek and got some rocks, and drove it back up without spinning a tire!
I don't normally let it get this tall, but being a long distance truck driver, I'm gone for 2-4 weeks at a time ... Some times I get to swing by 2-3 times a week, but this spring I was gone the full 4 weeks, and it had rained over 12" in that time, the grass grew!
I normally mow that first lap near the creek in 4X4, and very slowly, working my way along looking for "the edge" and any "potential problems" ... Slow is less likely to tip you over as you have more time to react to what you're seeing and feeling.
One of the advantages of the pivoting front axle, which would be the first one to find a chuck hole ... Is that it takes about 4" of rise or dip for my axle to "bottom out" on my frame, which then provides side to side stability ... So less than that won't cause any instability
IF you're going slow!
Very easy to test it on your own tractor, just get a few 2X's ... At 3" mine still has a little gap ...
But at 4.5" it's touching ... This will obviously be different on different tractors ...
On mine, it's the same on the back, 4.5" will cause the front axle to supply stability.
I'm not convinced that a tractor would tip over backwards with a brush hog on back of it going up a hill, possiblity of lifting the front tires? Maybe ... Unless dragging something like a back blade that snagged a big root ...
The advantage of driving forward up the hill is that the R1 tires the OP has are very directional, as in the "dig in" going forward ... They provide more traction going forward than backwards.