[racket] Decrease fontsize in @racketblock[..]

Hi,
    I am using Scribble to generate a racket piece of code in pdf, but
I have two questions:
-What is the syntax to decrease the fontsize in @racketblock[..]? Do
you have a small example? I tried with different syntax, but I
couldn't :(.
-What is the new line command in the code:comment function? I tried
with ~n, It does not work.

-- 
Saludos, Paul Leger