I have a few flip mirrors but the ones that get used the most are the Vixen in my WO 72FD, np there for guiding. It has the advantage of having a T thread on both outlets so I can use a variety of spacers to achieve focus depending on what camera/reticule I'm using.
I use a 1.25" Meade with my ED80 (with WO 10:1 focuser) if I'm guiding with that. It just works
The 2" I'll use for imaging with either SXVF-H9 or hopefully, the 20D through either the ED80 (fingers crossed) or a focally reduced 8" Meade.
I think I've got another one somewhere?....or maybe i lent it to someone. Can never have too many flip mirrors or reticules.