Have you taken G-regs advice? From what I've read, he is the only one that really answered your question.
Go to the CCC and look at the instructions yourself.
It seems as though you've figured most of this out, but here are a few examples to go by.....
Not sure what you're rate is, but there is a certain Master Chief that is at A school that went to Mast when he was in A school (he was a CL and tried to cover for a shipmate), long story short....learned from his mistakes and was successful.
I got to my sub out of prototype and we got a SPU about 6 months after that, he was coming to us as an E-4 (should have been an E-5), turns out he was Masted for blazing off signatures....came to the boat and HIT the books, qualified like a mad man and the CO suspended the bust....got back E-5 and his TIR!! He took the E-6 exam and made it. Only person that I have heard of to be an E-4, E-5 and E-6 all in one year.
There is life after Mast, some of the BEST nukes are those that have went to Mast (they have a better understanding for the pride in their work a little more).
Good luck, sounds like you will be fine.
Matt