CL300
Thanks for that, I will do some reading and see if I can't find out whether Vmu is a requirement for FAR23, I'll take a punt and say it isn't.
Regarding minimum Vmu speed I haven't tried to prematurely lift the aircraft off the runway but my gut instinct is that it could be done a few kts lower than the Vs speed, so perhaps a number of 68 kts at MTOW
The rest of your response eluded to the deeper reasoning of Vr that I am seeking. I have held a gut instinct that once the Vr speed has been placed in front of Vmca/Vmcg (clearly common sense) that the margin in front of the stall speed is some what superfluous.
Provided that separation does not occur until the stipulated Vr speed a safe margin is provided above the stall.
It seems intuitive to me that by stipulating a Vr speed the manufacturer obtains a known aircraft profile through the acceleration stage to lift off and as such is able to give repeatable accurate information on what point their aircraft will reach 50'.
CL300 I hope you add more to this as it appears you know a lot more.
Regards