...depending on your platform, this may not work for you.
For instance, on Solaris 9 and nagios 2.9 if you change MAX_PLUGINOUTPUT_LENGTH to 1028, recompile and then run the nagios config verify (i.e. nagios -v ) the following warning comes up:
Warning: Size of service_message struct (1192 bytes) is > POSIX-guaranteed atomic write size (512 bytes). Service checks results may get lost or mangled!
...in this case I recommend keeping the original value of 332.