Scanning truncated messages

[Alex]

Hi,
I've implemented a spamassassin plugin called ExtractText which
executes a remote script to scan PDFs and other documents for
potential malicious code or spam.

The problem is that amavis is forwarding to it documents that have
been truncated as per the $sa_mail_body_size_limit variable.

This results in my script failing because it can't operate on this
truncated PDF document.

Is there a way to bypass scanning of these messages beyond a certain
limit entirely?

Maybe it's instead possible to pass the size of the document to
spamassassin/ExtractText so I can make a determination from within my
script that analyzes the PDF documents?

Please help me understand what I'm missing.