hmmm,that's interesting. It seems to work a little better though if you go TMITMI.
You can't really do it too fast though cause your thumb and index (or middle depending on if your using the pattern TMI)will cancel each other out since there approaching the string from different directions.
I've always done it using RMI, you can play it faster that way and have your thumb free to do other things, like in Austurias.