I am looking to purchase a mower for personal use to mow a 7 acre yard. I tried several mowers last year and have decided on the exmark. I had intended on buying the 60" Z with a 27HP Kohler. I see now they have a 66" mower available that is only a few hundred more dollars with the same 27HP engine. My question is whether a 66" mower will be underpowered with the 27HP Kohler.