I have had a feature request for flash node to put upload limits in to control how much a user can upload in a single file, and in total - basically what the upload module does for other files.
I was going to lift the code from upload, mod it slightly to use a separate set of variables, and use that for flash node, but when I went looking behind the scenes I got a bit confused.
Flash node calls file_save_upload, and I can ask it to use file_validate_size to check limits. However, file_validate_size then calls file_space_used to work out how much the user already uploaded. That function tots up *everything* the user uploaded, not just files of a specific type or criteria (aside - does it? the code looks like it tries to do a user specific check if the uid is null and returns the total if a uid is given??)
Anyhow, if I supply a total upload limit specifically for flash node the limit might be reported as exceeded as a result of the user uploading other things in other modules. That implies to me that the upload maximum is a "global" setting since it is the total of all files that have been placed in the {files} table.