I think insta-adjust shifted to easily on the early eyepieces and got a bad reputation at that time, but it's been stiffened on more recent eyepieces. I can pick up my 22 Nagler without the housing shifting, unless I give it a slight shake. I keep the insta-adjust in the home position and could even use another mm or 2 of eye relief; I guess the preferred setting depends on whether you've got a face shaped like an owl or a face shaped like a witch
