I guess if you're only playing a few here there it might be worthwhile, but I can't understand the appeal of the double or nothings.
50% ITM and you're losing ground because of the rake. 5 of 9 ITM and you're barely covering the rake and a few pennies profit. 6 of 9 and you make a 'little' profit. How long can you sustain a 70%+ win/ITM rate?
I don't play the double or nothings, and I don't play the FT matrix games either, but aren't the matrix games a better probable return especially if you can sustain a constant 60-70% ITM rate? Reason I don't play them is because of the math behind the payouts, but that's just me.
If you e-mail FT support, maybe they could give you a clue. Would also let them know of your interest in them.