I am a homeowner looking at a new Hustler Super Z with a 72" XR-7 but can't decide on which engine to get! I would like the 26 HP Liquid cooled Kawasaki(quiter,fuel effient, longivity) but I don't know if it will be underpowered? I've been reading a lot about the 28HP Kohler EFI but I not exactly sure about kohlers and being air cooled! Right now I have a Grass Hopper with 21 HP LC Kubota diesel and a 61" deck and it is way under powered. I mow about 4 acres and it is mostly flat and not many trees. Which engine would you guys go with? P.S. I know the 72" deck is overkill, but I value my time!!!!!