Is there any way to limit upload size RELIABLY using Apache and Mongrel BEFORE upload completes?

I posted an issue yesterday, and perhaps I did not post it clearly
enough. I am curious to see if it is possible to limit a file upload
reliably so that someone does not try to upload a 100mb or 1gb photo
for example. Attachment_fu and file_column and even paperclip can be
used to do this on the server side, I think AFTER the upload has
occurred.

SWF upload can do this on the client side, but we don't have a whole
lot of control on the client side, and I do not know how much I would
like to depend on flash.

I would typically use LimitRequestBody on the APache config file, but
since I use several mongrels via a proxy load balancer, the
LimitRequestBody is useless since the request bypasses typical Apache
protective mechanisms and is sent to mongrel.

Is there any way to limit upload size RELIABLY using Apache and
Mongrel BEFORE upload completes?

David