Hello Contours , There are some members on this forum who are tired of this topic. I am not however. So I will keep it short and concise. When the 961 oil tank is overfilled , it will push/spill oil back to the back of the head where the oil tank vent pipe goes. Then it is made available to flow back down the push rod tunnels to return to the sump for pumping back to the tank. BUT , that oil is also made more available to escape through the valve cover breather banjo and into the air box where it will need to be drained periodically. SO , the longer , re-marked stick lowers the oil level in the tank so it doesn't as readily get pushed/spilled out of the tank breather and ultimately there is less oil coming out of the rocker breather banjo and into the air box.
For most folks this is enough , but I will continue . The Norton Factory having realized this have developed a different breather system . You have seen it already I am sure. The most tell tale sign is the oil/air separator box in the breather pipe going from the crankcase to the air box. This update requires the fitting of oil feed valve and return line check valves , screen filters , rocker cover banjos blocked and the oil/air separator installed. When the kit is fitted as directed by the factory , periodic draining of the air box oil is virtually eliminated .
The short answer is YOU DON'T NEED THE NEW DIP STICK. I want one though .