What would you recommend I put for the 'maximum message length' count?

[Deities]

Well it depends, some people need walls of text but others just spam and to take a full post of spam is horrible. It depends if you will ban the spammers then set it high, if you want a clean and automatic forum that cares for itself then set it to allow a littlebit more than a tutorials length. (where they can then Double Post for more)