Hello ShowroomShine, why do you want mow this area? It does not make economic sence. You would be better off to plant in a timber trees or otherwise retire that slope. To me mowing this slope is an unneccesary risk if you are unsure about your skill level.
The photo clearly shows the safe area to mow.
Alternative, Is your neighbour a stock farmer? If so ask them to graze the steep slopes for you. A trough for water and a single wire temporary hot wire (electric fence) and the slope is mowed by the stock.
If you do use a tractor, then use adjustable rear rims set to maximum width OR go DUAL wheels. HUGE difference in stability and traction.
MF 135, standard track is 6 ft wide(est), same rims set to maximum widthis approximatly 8 ft. I had an MF 135 with the rims set to 7'6" (so it could drive onto the tip truck with the sides on as it was carted between farms) .