asterisk users - Aug 2009 - password length of sip peer

I'm trying to figure out the maximum length of a cisco 7960 password
in the SIP<mac>.cfg file. An Aastra9133i can take at least a
36-character password, but the cisco craps out (can't authenticate)

In order to stop me from doing a brute-force test, does anyone know
the password lengths of

Aastra 9133i
Grandstream gxp2010
Cisco 7960/7940 ?

Julian