For now, no, it has to be 9999.  I can probably change this or get rid of that requirement altogether.  I don't understand why the coin formerly known as darkcoin came up with that requirement to begin with, I guess it was to ensure you could get a direct connection.  There are better ways to handle that peer negotiation IMHO and make it more automated.  Masternode should be able to be a peer like any other, we already know its address, port should be irrelevant we could just match the address and handshake with it.  But that's future enhancement.