Reading the
Agena add for Meade 4000 series FF/FR, they are now recommending 85 mm working distance (backfocus), just as Celestron (Bintel).
Picture of image train on Agena site is misleading and actually plain wrong (attached from their website). It should look more like the second picture (with ~30mm extender, not ~60 mm)
I am pretty sure, 3 years ago (and
recently on Agena) suggested value was 105 mm (also
mentioned on CN couple of times, even last year).