It's quite simple really to add more or limit characters. All you have to do is check all the .cgi files for this line:
SIZE= is the size of the inputfield, you can leave that one alone.
MAXSIZE= says howmany characters the username can be, so you can alter the number.
This goes for all inputfields btw. Make sure you check all .cgi files and dont forget one. I just had the stupid problem someone registering a username longer than 30 characters but then he could not post anything because there was no field where he could enter his full username

Benito Mauro Maria Correira da Silva... Who the hell comes up with those names

lol