I have one really nice Bahia field that I cut at 5.2 to 6.5 MPH depending on the ground. I use a Krone EC 283, 9'2" cut, behind a 100 HP tractor. The Krone is shaft driven, no belts to slip. If I get in thick Bahia with our Kuhn and try to mow fast the belts will slip.
I only get about 30 acres...