Thanks for all the info folks. A lot of new information.
Believe me, mowing grass is the least of my worries. We already have the Huskvee, which does the job mowing, except on the two grass slopes that are 50% (per the chart posted above). Right now I do one of them with the Huskvee (downhill only, and thank God for the new road that cuts across, making a landing/turning-around space right before the 75% drop off--some pucker factor there). The other one doesn't have a good "landing place"; it ends in tall trees. No where to turn around, can't back up, can't go forward, can't turn around..... I pay someone to mow that one now. Would like to clear a landing place/turning around place there too; but if I have to, I'll let it revert to wild
Frankly I don't much care about grass lawns....just a little around the house is fine and I ain't that picky. This isn't a golf course. There's only so much effort I'll put into farming something I can't eat, like tall fescue.
Really my main need is expanding the garden/orchard, or should I say "carving it out of the mountainside"; maintaining the long gravel driveway, the even longer steep road to the ponds, the paths around the ponds, and the trails all through the woods. Some of this is now just maintenance, thanks to hours/days/weeks of backbreaking work with shovel and rake. But a lot of it is making new. When I bought it, this property was a couple acres of weedy grass surrounded by 16 acres of Vietnam jungle--I'm sure you can relate. Former owners were city folks who never left the house except to mow the lawn. I want to leave a lot natural, but I'd like to be able to SEE some of it for one, and have at least a small path to walk all around it. Plus, let's face it, this is second-growth forest, and keeping some of poplars cleared out helps the hickories, chestnuts, black walnuts, come back. Not to mention our native (and rare) red pines. Can't let the poplars choke them all out. I also feel that by clearing out the ravine and spring, getting it flowing again, and creating ponds, has also created new habitat, as well as being nice to look at.