There are no M values for "B" and "C" variants in regards to Helium (only nitrogen. The "A" variant Helium component was derived from the Nitrogen component ratios)... sadly Buhlman passed away before getting down to modifying those like he did with the "B" and "C" (making them more conservative in the "fast/mid" tissues). So all devices using a ZH-L16 algorithm (in whichever flavour) reference the original Helium values (unless they've gone and made their own values).
The C variant was intended for dive computer use, as it would track the actual dive better.
_R
Indeed.
So in summary, the right N2 coefficients may well be wrong but the wrong He coefficients might be right.