If you don't mind departing from the true classical Heron image then a much larger one may be used which will improve boat control and performance.  This is because it allows the helm to sit well forward which lift the transom clear of the water and so reduces drag.

With the standard till an extension length of 750mm (30inches) is OK.  I have used a modern rubber flexible joint for several years and have found it far easier for use than the various metal/plastic swivel types.  But I am still wondering how long the rubber will last!