It depends on how often you are mowing that field. If you are letting it grow to 2' to 4' tall and knocking it down, get something that covers your wheel tracks and plan on going slow. If you are mowing it every 2 weeks or less, you could handle a 7' machine. I'm the same hp range and pull a Ford 917 which is 6.5' wide. Don' know its back there for 6" or less grass but when I mow the neighbor's horse lots (no horse anymore) that is 3' tall alfalfa and clover, its slow at best. If you are not concerned about the finished look, go with the heavier "Y" blades. They last a long time and are mostly rock proof. I'm looking to upgrade to a 918H in a 6' model, but haven't found one yet. My 2 cents and I'm sure you have pocket change after a day or so. Find a dealer and ask for a demo.