[mod_python] File upload limits

I am writing a Web application which requires the user to upload a file.

It seems sensible to me to limit how large the file upload can be. After
searching around it seems that I need to modify Apache's content-length
attribute and that mod_python is what I should look at.

It would be nice if the FieldStorage class:
http://www.modpython.org/live/current/doc-html/pyapi-util-fstor-fld.html
Had an input limit, because I can't see one.

Does anyone have an example of this type of input checking I am after?