In the new responsive designer, you have the ability to set the allowed max size per file uploaded, as well as the max number of files. The highest you can set these limits is 25MB and 25 files, respectively.

I tried pushing this by adding 3 large attachments (approx. 13.4MB, 12.6MB and 4.6MB) to a file upload control.

When I tried to submit, the form hung on the loading screen. The data did get sent to SharePoint after a few seconds though. The workflow was also triggered even though the form was still "submitting." The form hung for like 10 minutes or so before I closed the browser. While the form data had made it, only one of the attachments was there and it was unreadable.

Does anyone know if there is a "best practice" for combined amount of file sizes in one file upload control?

Technically, what I uploaded was under the max limits, but clearly there were performance issues.

I'd like to have a ballpark idea of the total MB to stay under, so that I can relay this to users as this form is rolled out.