Comment Limitation

Hi there,
I have a website, VINTAR.COM hosted by SURFBETS.NET, and elected to have ADVANCED GUESTBOOK.
The issue I am having is this: In the message form, there is a limitation of text that could be entered, and this can be
controlled thru Admin. This is fine. However, in the comment form, there is no limitation of text that could be entered.

So, what is happening in my guestbook, is that when the users discovered that there's no limit on the comment form,
they are using this, instead of the message form, and enter huge amount of text.

Like the message form, I would like to have a limit on the comment form also. Otherwise, I would easily exceed the disk
space capacity alloted to my website.

Thanks for your support .......