At what level of confluency should the SkMC differentiation typically be initiated?

We have obtained best results when the cells have reached 60-80 % confluency. At this point the Growth Medium is aspirated and replaced by Skeletal Muscle Differentiation Medium. After 2 - 8 days extensive formation of multinucleated syncytia can be observed. For a stable differentiation of SkMC switch back to Skeletal Muscle Cell Growth Medium after 5 days incubation in Skeletal Muscle Differentiation Medium.