John, Jimmy’s information re the 146 is correct. Whilst NWS is not an issue, the side force available from the nose wheels is. It would be possible to use the lower value of Vmcg at lower wts if the full effect of forward stick was allowed during the take off run. However, this was not possible as the certification requirements for control jam during take off limit the stick position to the mid range. 146/RJ operators note the AFM requirements for stick position during takeoff as this not only affects flight control in the event of a jam, but also the ability to maintain directional control on the runway, particularly when at light weight.
Another interesting effect was utilised by the HS125, in which the lateral / directional characteristics enabled the aircraft to be steered on the ground by the ailerons. I believe some credit was taken for this in the calculation of Vmcg.