[Zope] How to stop users uploading large images

Hi Folks, I want to allow ordinary, low-privalidged but non-anonymous users of my site to upload small images. I can use PIL to scale images that are slightly too large. However, I want to stop users abusing the system by uploading 100MB images to see if it will crash the system. What is the best way of doing this? Can I modify the _read_data() method of lib/python/OFS/Image.py to read some kind of maximum-size attribute, and abort uploads that exceed that size? Alternatively, perhaps this is something I don't need to worry about. Maybe the ZODB has a graceful failure mode on extra-large uploads. -- Steve Alexander Cat-Box limited