Wow that's quite a site. Thanks for the suggestion.
The secret to an accurate calculation is understanding that the tire size you enter is not the one on the side wall. The size that matters is the radius from the ground to the hub center x2. Keep this in mind when you are estimating larger tire sizes.
You can also arrive at your hub height by entering your existing numbers into the calculator and adjust the tire size until the calculator matches what you see on the gauge cluster for a certain speed.
FWiW, mine is setup for 3k rpm at 75mph.