As users will be aware, the 200mm extension piece uses three M5 bolts top and bottom to fit the EQ tripod/ EQ head.
When mounted, the bottom bolts are held securely with the central bolt tension.
The top bolts however only locate in the EQ head with no longitudinal pressure to "lock" them in the slightly oversized holes.
The reason for mentioning this is that I use the extension on the top of a permanent pier.....
The last few sessions have given me poor guiding and poor GOTO...
Upon checking the PA (which when last checked a year ago was within 10 arc sec) showed the polar axis had dropped 1.5 degree
Unbelievable!!
Trace the issue to the head droop on the top of the extension. The mount holds a fair load - C11+spectroscope+electronic finder+ 4 cameras and 25Kg counterweights.
It seems impossible to "pre-load" the top bolts to give more rigidity.
The mount has now been realigned and the PHD and GOTO issues have gone away.