I'm not sure if this is done automatically but in my startup command line I have in exec server.cfg so each time the server is started that file is executed. Also, forget about the server_cfg, I'm not even really sure why that is there either but it's not the standard way servers are run. Use the server.cfg and add the line "net_maxfilesize" "55" Also make sure that you are not using the sv_downloadurl in there as the two will conflict.
And just a heads up, you really shouldn't be sending the maps from your server as you are, the sv_downloadurl is a much better way of doing it but you'll need webhosting of some sort for that.