Just to chime in, I have two Woods RM990's which I run on tractors with 28, 34, 37, and 49 pto hp. The RM990 is a commercial-quality rugged unit with swing-back blades - well-suited to former orchard (rock farm) converted to uniform grassland. Even the smallest tractor handles the RM990's ok, though if the crop is extra dense or wet it needs to go slower for a full-width cut.