I'm still a bit puzzled as to why you can't get focus on mid or high powers ??
May be worth asking on the CN forum (bino-viewers). 'Eddgie' who is the expert on there may be able to help.
If you could post a pic of this alledged 'sag', that would be useful.
I went for the Moonlite CR2 from FLO, but with the non standard extra long drawtube. Mine is a 60mm, and they used to do a 70mm as well.
As these are non standard there may a wait to get one shipped in from the US (a month or so)
However, the 'standard' 50mm will probably be ok : If you use the large 1" spacer or both the 1" and 1/2" that they supply.
Another possible option is to raise the primary up to its higher setting (OO have 2 different settings for this ; mine does)
Its a bit of a trial and error thing with a bino / powerswitch / newt setup. A bit of a juggling act.
What you want to look for is being able to get the low power switch to focus as 'close in as you can' by either raising the primary or trying different focuser spacer options etc.
You can of course simply adjust the OCS position to do this, but remember, the further out you set it the higher the base power will be, ie it won't be the advertised 1.2 or 1.3x
but more like 1.4x or 1.5x. And we want our low power to be as low as we can for those wide field, rich field views. Its quite a feat to be able to get 60x with a 12" Newt with a binoviewer.
Post some pics and keep us posted with how you get on.
https://www.firstlightoptics.com/moonlite-focusers/moonlite-cr-dual-rate-tri-knob-crayford-focuser-for-newtonians.html