Hi Deejay,
A quick test run has been done and I am happy to report that the mower achieved a max speed of 2.5kts.
The downside of using my windsurfing gps data logger is the readout is in knots - and 2.5kts is certainly a long way short of my windsurfing personal best of 34kts.
With a 1:1.852 conversion ratio this is about 4.6kmh . I found this to be a very comfortable walking pace, maybe even a little too comfortable for me.
I will do a better test run when I have more time and will pay closer attention to engine speed. I am not sure of the actual engine speed when the max drive speed was achieved but I reckon it was closer to 3000rpm than 2000rpm.