My Zenithstar 61 is one of the original type with just the small foot adapter for mounting and no guidescope socket.
While fine for visual this has way too much flex for imaging use once a field flattener and a cooled camera or DSLR gets added to the OTA.

I decided to upgrade to the new version double ring and cat handle, but had to wait some time for the matching Gold version to come back into stock.
FLO finally got one in stock so I ordered and it soon arrived and proved to be very simple to add to my Z61.
Fits easily to the main OTA. (which is not the same place as the foot style adapter which sits on the focuser section).
The FLO page for the upgrade has good clear diagrams to show you how to correctly fit this new set of rings.
As usual for William Optics the build quality is very high , I now cannot flex the mount at all.
I have the matched WO 50mm guidescope and this fits the CAT handle perfectly..

A very worthwhile upgrade if you have one of the early models Z61.
(I also added the matching 245mm WO vixen style bar)

Pleased with this, does the job, needs a bolt provided so you can attach to WO bar.

The ring arrived quickly and was well packed as usual for FLO. Simple to install - I would mention that the focuser is threaded - so it is unscrew rather than 'twist' - but I guess they are the same thing really. Once mounted I added a WO DSD Plate (210mm) and it is now rock steady on my mount. The original photo type mount had some flex in it, which this fixes, so well worth it.