how steep exactly? We do one twice a year. It's just over an acre. At some parts, it's so steep that you are almost guaranteed to slip down. During the first whacking in late June, all the foliage is thick and growing (loaded with water, and about 60-70% of the area has an underlying ground cover of poison ivy). It takes longer to cut. Takes two guys about 6-6.5 hours. During the second whacking in mid-late November, most everything is dead/dormant so it goes faster. Closer to 4-4.5 hours. The key is whack it as low as possible each time, makes it easier on following whackings.
GM trucks, Scag & Yazoo/Kees mowers, Shindaiwa, Redmax