If M4's head is anything like V4, it's very difficult, if not impossible, to fit some of the hair models made for other figures, to them.

I can pretty much get any hair model to fit V3 or M3, but there are some models that I just can't get to fit using only the dials.  I suppose magnets would be a good option, but while I know how to use them I'm still not very good with them.

Wardrobe Wizard is an option if you have it.  Though I find that for some reason I often have trouble converting hair and many times it ends up "short".

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi