UPDATE: Well, started tilling tonight. Piece of cake! Several baseball to softball sized stones. No problem. Tiller has slip clutch which I checked to make sure it would slip per manual before proceeding. The area I tilled was former hayfield that I claimed as part of my yard last year. So, it was just grass--and very little of it since we are just starting to see green this week. Made 4 passes at 3-4" deep. Plan to go deeper in the next few days. No tangles. No stones in tiller. No clumps. Probably gonna be another 3-4 weeks until we can plant up here.