I'm taking it as he was thinking I'm haulin a$$,  but really doesn't seem that fast in heavy hay. 

To accomplish 60 bales per hour, I will admit to having long, heavy windrows.  This year we traded up to a 568 JD baler, with 1000rpm, netwrap, hyd pickup, high moisture kit, and large tires (no kicker, too much steep ground here where it can't be used anyway).  Pulled it with a 7610 JD mfwd with PS trans, usually around 800-850 pto rpm, and about 7 to 7.5 mph, occasionally a little faster depending on conditions. 

Set the monitor to go off at 68.0 to 69.0 inches and when it signals bale has reached full size, pull shifter straight to neutral, hit the brakes, and by the time you're stopped the bale is right at 72.0 inches (occasionally, it'll hit 72.5 or 73.0 [happened 3 times I think this year] but I try and avoid that).

Only time I stop is when I'm reversing direction, or dumping a bale on steep ground, and I rarely ever use the clutch.