Yeah, I was trying to figure out why it had that "servercfgdefault" in there. It turns out that is only used when you install so that it copies the contents of server.cfg into csserver.cfg (this name is the "servercfg" variable). The parameters used when the server start are on
this line and it specifies the the variable ${servercfg} to be set as the servercfgfile.
Regarding download speeds, there is a bug with fast download where if you get disconnected once while connecting to the server, it will fall back to downloading directly from the server (which is naturally slow) i.e. skipping fast download. The only way to recover from this bug is to close the game and then start it again (on the client side). You can test this theory by setting the server cvar sv_allowdownload to 0.
If this bug is occurring, those people will not be able to download from the server at all. Having this turned off is generally not recommended because it requires that your fast download server files be perfectly aligned the server files but it can be used as a debugging step. So, find someone who has the issue happen often and see if they get a message that says that they can't download from the server directly.