WELL, if I had remembered(old man issue) that you had previously posted about the Big Bee then I would have known what you were working with

Is your tractor a hydrostatic type transmission or Gear type(with a clutch)? Never mowed with a Hydro so I can only tell you about the gear type. IF a hill is steep enough, and yours doesn't
appear to be terribly steep, you can get pushed down a hill while mowing, been there-done that, due to the momentum of the mower spinning and higher than normal RPM EVEN with LIVE PTO, overcoming the rear tire traction. That being said IF you feel uncomfortable going down a hill, reduce the RPM's a bit or even IDLE to maintain control then
gently apply brakes then clutch if you have it, or drop a gear with a Hydro. The mower stays in the same position either way. With your lift type mower I would keep it in the mowing position on any slope, don't need to raise it to turn most of the time. Doing so takes weight OFF of the front axle and
may cause some steering issues. A LOT of mower manufacturers say to mow UP and DOWN the slope. If I did that I would end up in a sink hole or ditch most every time. I've ALWAYS mowed across the slope on my steep ground but I have the wheels adjusted to nearly the limit(wide) and have over 250 pounds of weight hanging on the front of the tractor AND I use a pull type mower versus a lift type, the weight on the drawbar is always there. Never had a ROPS and never really wanted one either but that is an OPINION. If I had your tractor I would be using the seatbelt though. I DON'T think you'll have any issues given your land and your approach to it. Good Luck, take your time and be cautious