Thanks chaps, I appreciate your feedback.
The weather is threatening to be clear tomorrow night so I will try and give it a go. I'm already running 3.35 and as I've been polar aligning by eye to less than 1 degree of error in either axis I've not been using the polar alignment routine. I'm not guiding, so I guess I'm introducing the error by not aligning well enough
Will try on a star ASAP and see what happens... with my planetary camera and powermate I'm basically running at about 1000x, so the effect is amplified but my DSO images have showed trails too. I need to practice drift alignment too...