After excellent advice from the folks at FLO I upgraded my small guide scope to this OAG.
It was easy to set up with my 6" RC and is giving me round stars once I got PHD settings correct (the only fiddly bit).
The prism is small so a sensitive guide camera is needed. I'm using an Atik 314L and still only get a couple of guide stars depending on where it's pointing.
The included accessories are useful for getting it all connected with the telescope.
Thanks again FLO

FLO were great as always, took a while for me to work out how to focus it (no instructions as is the way from ASI) and that the ASI 120MM should be used on this without the black spacer (I am a slow learner!) so that the chip is right on top of the aperture on the OAG and in the same orientation as the aperture which is obvious with hindsight but, when eventually I got it going, it was great and saves worrying about knocking the traditional guide scope off line as a bonus.

I found that when the lock screws are tightened, the OAG can nove in its machined slot, which is obviously a big no no. Perhaps mine is faulty....

Positive experience all around.Easy to set up during the day.Attain good guiding figures at night.There was less guide stars as is widely documented with OAGs but i had enough,at least with my chosen target(M51)in my field of view.Used with a QHY5L II MONO ( which i believe has the same sensor size as a asi120mm mini) and an eq5. sub arc second guiding all night @ 1280mm focal length.Thnks as always to flo for quick service.

Fantastic service again from FLO. They are my go to supplier for all things telescope. The zwo oag was really easy to set up, just waiting for clear sky’s to give it a run.

The ZWO off-axis guider is a lightweight, well constructed instrument. It was easy to incorporate into my current set up, simply replacing the 16.5mm spacer between my Skywatcher ED80 telescope and filter wheel. It arrived promptly from FLO in their usual high standard of packaging.

However in use things proved more tricky. Whereas my ZWO Miniscope picks up lots of stars and I get guiding straightaway, there are of course fewer stars with the OAG. Guiding with the ASIair, and ASI120MM guide stars are getting lost. I am still experimenting, but suspect unless you have a really dark sky the prospective guide star quickly gets lost in the 'murk' of light pollution etc. So the OAG loses a star in this review!

I was having trouble with flexure using a WO 72mmX 420 guide scope, with my 8" edge HD. This was easy to install and immediately solved the problem. The guide stars look like bananas but is not effecting the guiding performance. I am using the asi120mm guide camera and need to run it with a very high gain to get more guide stars. The guiding figures are the same for both OAG and guide scope but my stars are now round and zero field drift.

I married this OHG to an Atik EFW2 filter wheel. I contemplated drilling and tapping the OHG body to make use of the three screws in the EFW. These screws are the ones used by Atik for their OHG.
In the end I ordered an male/female thread adapter from Flow. To be able to fix the orientation of the guide camera by setting the height of these three screws. Focusing has been initially set in daylight using a distant tree so we are waiting for clear night for further focusing and testing.