Matty, you havent mentioned the sub exposure time you used, sheesh, thats fairly critical to analysing your mount performance
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Have your OTA sightly off balance to avoid backlash (RA), it should always "drive forward". Eggy stars then can be reduced in PS.
Differential flexure can be reduced by mounting the guide scope directly to the OTA (if it isnt) and bolting the guide cam to the guide cam rail too. I image at 3050mm FL with external guide to 20mins this way.