I have continued experimenting and have still found no solution. I tried synching across ports on 2 different machines. db1:3308 -> db2:3307 does not work; records get placed into db2:3308.
I still believe that the port that is used on connection for the source machine is ALWAYS used as the port for the destination machine. To me this seems like a bug (as both ports are asked for separately). I don't know how difficult this will be to fix, but if a fix is not in the works I will need to look for another solution.