Well, I believe the max post size is limited by the max size the field type in the database allows. Which in this case is the "text" type which is designed to allow very large portions of text to be inserted.

I believe he "max size" of the common "text" field in a MySQL database is 65535 characters

I am a Web Development Contractor, I do not work for UBBCentral. I have provided free User to User Support since the beginning of these support forums.
Do you need Forum Install or Upgrade Services?
Forums: A Gardeners Forum
UBB.threads: UBBWiki, UBB Styles, UBB.Sitemaps
Longtime Supporter & Resident Post-A-Holic
VNC Web Services: Code Modifications, Upgrades, Styling, Coding Services, Disaster Recovery, and more!