<<The Mark II tail alone exacerbates flight problems at rearward CGs since it adds such a large rearward moment.  Thus the corollary recommendation that the long engine mount be used to move the CG forward.>>

Scott,

The longer engine mounts serves to move the CG forward.  The increased surface area of the MKII tail moves the neutral point rearward.  The difference between these two defines the static margin.  As the static margin goes to zero, the aircraft becomes neutrally stable.  This means the MKII tail can handle a more rearward CG than the original for the same degree of stability or conversely, has greater pitch stability for the the same CG location.   

Two side notes:  The long engine mount is actually somewhat destabilizing in yaw and pitch due to the added surface area projected out in front of the CG.  The larger tail can also handle a more forward CG since it has more pitch authority at low speeds. 

The added area in the tail simply opens up the available CG range in both directions.  Either tail may be perfectly acceptable as long as each is kept within its individual CG capability.
Chris

 

 

 

Chris Zavatson

N91CZ

360std