@ Mutt
Xwind has no affect on Vmcg.
If I were being incredibly pedantic I'd agree with the statement. Vmcg is defined, for certification, for a specific (zero) xwind. So, technically, the declared Vmcg doesn't change with Xwind.
But, the real speed at which the equivalent conditions of Vmcg are met certainly does vary with Xwind, which is what you are saying, and I'll heartily agree with that; only a bloody idiot would go do Vmcg testing in any kind of significant Xwind.