If the mode(s) that you are applying are not being kept, try checking with chanserv to see what (if any) modes are locked using mlock.
If the mode(s) that you are trying to set are being countered by chanserv's mlock, then you need to find out who has access to change the mlock options on chanserv for the channel in question.
That's the only thing I can think of that would keep the code you posted from working.
Most servers are running separate from services, so any command you type to services needs to be forwarded on by the server. This leads to an increased latency for messages bound to the services. If you consider this, then no, that code wouldn't work. Unless you define a working solution as one that works only when the conditions are in your favour (which certainly isn't my case).
