Paul, my guidescope is 20cm long, with a non-rotating helical focuser - no sag anywhere. No issue demounting and remounting the guidescope either - see picture (finder shoes with a long finder dovetail secured to the finder rings). I have demounted and remounted the guidescope probably 20 or 30 times, and I have never had to readjust the alignment - it maintains alignment each and every time.
Main reason I keep it now is for polar alignment with Sharpcap seeing it is a portable setup (and a genuine dislike of the QHY Polemaster). I will try to see if the OAG will be useable for polar aligning, but I have my doubts. The FOV last time I used it was so small as to not show Canopus in the OAG frame at all, despite being perfectly centred in the main camera and guidescope. Plenty of stars - more than enough for guiding - just not for PA
