First off, I am extremely happy with the free service of Cloudflare and I would recommend it to anyone wanting to get some free SSL's for personal projects or really anything.
With that being said I ran into a problem last night while trying to upload a large video file for a new project using a front end I had created. After doing some reason I found that with their free account user's can upload 100mb's of data at once. Thus if you have a large file bigger than 100mb's you are left with two options.
What you can do is build a different portion of your website (such as uploading files) that will not be controlled by Cloudflare's DNS. This will let you go past your limit of the 100mb's and upload pretty much any file you want (according to your server setup).
While on multiple chat channels people seem to forget about the old school methods that some of us developers had to put up with and still do today. One of them would be to upload the file on to the server by method of SFTP or another protocol and then create the record manually.
When all is said and done it took me awhile to find the limits of Cloudflare's DNS control and even though their limits are pretty small I still love what they do and I wanted to bring attention to their current limits and hope to raise some awareness to the mysterious "413 Request Entity Too Large - Cloudflare nginx"