Good to see another MN haircut thread. Great reading 
I've been doing mine since the first thread so a couple of years at least, hair is poker straight and fine. Totally unforgiving. First time I did it my uber critical snob of a MIL wanted to know why I'd been wasting money on 'an obviously expensive cut' while we were so skint...
The thing with the basic MN cut is that to loose any length on the underneath layers at the back you have to start with really long hair and cut masses off. Simple maths - 'tis quite a long way from the nape of the neck to teh hairline at the front, then you've got the ponytail length too.
So, yeah, I do an adapted MN cut so I don't end up with a ratty tatty bottom layer. Hair is +/- bra band length so not short as such.
I always do the all-in-one-ponytail-right-on-hairline cut first. Then I section off my hair to do the bottom / back 1/3. Put the front out of the way in bunches to each side and make a ponytail right at the top of the back section, pull it to the front (along my parting) and chop, snip, snip, stab, sorted.
Then, 'cause I like my hair long but with layers around the face I section of the front of my hair (from in front of ears) do another ponytail.
The snip snip stab stab bit is really, really important. The more attention you pay to it the better it'll look. Neatness of ponytail is vital too, on my straight hair anyway, maybe less so with curls.