I am planning to purchase a grasshopper frontmount mower for my 6 acres with 4 - plank fencing. I, like everyone else, would like to mow as quickly as possible realizing there are limitations involving the roughness of terrain, type of grass, height of grass, and moisture content, etc. All those things considered, which of the grasshopper engines in the 700 series is least likely to lose RPM's when the grass is lush or a bit taller than it should be? I like diesel engines but the 21hp and 22hp kubota engines sound a bit light as the recent trend in mowers is toward higher horsepower. The 27hp Kohler has been around a while. The 3 cylinder 29hp kubota gas engine sounds interesting. I will not have the opportunity to demo all of these to compare side-by-side. The help of experienced operators would be appreciated.