How to choose the size of the mouthpieces

[maest...@live.it]

Hello, my name is Luca and I'm contacting you from Italy.

How anticipated by the subject of the discussion,I'm writing to you because I would like advice on choosing the two mouthpieces.

I've never had a Quadstick and so it would be the first time,so before I send it to the United States I would like to be sure not to make mistakes in the last details of the order.

I am undecided because the biggest measure would be fine for me as a beginner, but not having neck movement problems, I would'nt like to give me big speed problems if I become more practical.Is it so complicated to use the narrower one(26 mm) in the beginning?

Finally, is it so important to indicate the default configuration for primary device?

Thank you very much

P.s.:Sorry for my English ... It sucks : :-P