I have finally thanks to your advice and my friend here in Aus worked out how to connect twin rudders so that they operate as they should with good turn to port and starboard. To do this all I had to do was make a longer servo arm which created the correct arch so that I got max turn in either direction, see image attached.
I also note another issue when full stick to go forward it behaves as if its in reverse and full stick in reverse it is behaving like it should in forward motion very fast, should I reverse the propellers as well as change the polarity of the motors to correct the above, thanks in advance to your advice.