I have used an all Mavic Vitus 979 with Matrix ISO C rims at L'Eroica California and Gaiole in 2015. This month I am rebuilding the wheels with new spokes, as the old ones are brittle and I have popped a few. So I am rebuilding the front wheel first, but something does not look right. It turns out I have a 28 hole front wheel, in violation of the 32 or 36 hole rule. So don't tell anyone, I'm going to use it anyway this October.
PS: Anyone need 33 291mm DT Revoultion spokes? This works for a front 32 hole Mavic 501, Matrix ISO C, 3x.