Thanks for the info. Personally, I think a user selectable number would be better, or maybe 99MPH. Even though the highest "speed limit" sign might be 80 in the US and flow of traffic might be 75-85 in many places, it's important that the acceleration be there if needed in an emergency.
I say this with "my friend" having received a criminal speeding ticket in Arizona, a Class 3 Misdemeanor.
Speed limit mode would also work better with a city/highway or "over posted" setting to reduce the likelihood of someone going 99MPH in a area with a 45, or worse lower speed limit.