On perfectly flat ground swivel casters would probably work OK but, if you are working on any kind of a slope, and I am not talking about something that is so steep that you risk turning the tractor on it's side, the cutter will tend to want to go to the down hill side. Case in point; When I was at home on the farm we had a 5' rotary cutter that was 3PH. It had the usual swivel caster in the rear. We used it a lot in the fall and spring for chopping corn stalks before plowing. I always liked to use it with swaybars installed so that it would track straight behind the Ford when going up, down and sideways on our rolling ground. The same rolling ground that we plowed, planted, picked corn, baled hay and combined on. Nothing really steep at all. Without the swaybars on the tractor it was not unusual to completely miss one of the two rows I was chopping due to the cutter swaying downhill. This may sound like it was my fault for not paying attention to what I was doing and driving uphill a little to compensate. However, when you are driving at 4 MPH for hours at a time straddling two 1/4 to 1/2 mile long rows of picked corn, your mind tends to wander. /forums/images/graemlins/tongue.gif My dad didn't seem to think that was a good excuse though so my answer was to put the sway bars on. I am only using this example to emphasize the problem that caster wheels on a pull type implement would cause. The 3PH cutter was limited in it's ability to track off line by the limited sway in the 3PH itself. A pull type cutter with caster wheels would have nothing except the tongue to limit it's travel off line and could possibly sway up to 90* off the center line of pull or until it hit the tires of the tractor. I don't think the u-joints in the PTO shaft would like it very much, either. I just do not think a pull type, rear swivel caster cutter would be anything less than totally frustrating to use, the KK manual and WalMart shopping cart example notwithstanding. Just my HO.