I don't know about Farris mowers. But I have recently mowed with a Scagg Cheetah. I have clocked it without blades engaged at 12.4 mph low range. And 15.9 mph high range. I did mow some fairly rough land close to top speed low range. I had a chance to mow some fairly smooth land at top speed high range. WOW! Now on my own mower, a Bad Boy Pup, on my own land that is fairly rough, I probably mow at 6 mph until the Bahia Grass starts putting up seed shoots. Then my speeds slow down. I do lower my air pressures at 8 to 10 psi helping to smooth out the ride. Nice mow you have there!