I've always felt accomplishing loading Rails from a shell script was ugly too. I've always known about Rails runner command but never thought of putting into shebang line. I wonder if that is something new in Rails or if Rails runner has always been compatible with doing that. Very cool.
I think it might be worth mentioning that a 4G max on the client body size seems unnecessarily large to me for the average application. Maybe some apps could require such a sizable content transmission. I think being a little more conservative here could reduce exposure to easy DoS attacks. For example in the case I am currently building for even where PDF documents will regularly be transmitted in via API a 10M max seems totally viable.
I'm not knocking the author nor the configuration, it may be entirely valid and my concerns could be void as I'm far from masterfully knowledgable with Nginx.