MFS,
Just to clear my mind on a couple of things ...
(a) if you are, instead, Vmcg limited at light weight then you should have the unexpected effect of decreasing V2 with increasing weight
I presume that you are referring to the achieved speed being above book speed here. If you mean otherwise, perhaps you could amplify the point ?
(b) I've seen charts where V2 at min TOW was actually higher than at max TOW
I've not come across this ... again, perhaps you could amplify the point ? I presume that you are referring to scheduled V2 here ?