I was browsing this post and it reminded me that I have difficulty tightening the retaining screw that holds my binoviewers in place. The problem is that the screw is too short and is difficult to tighten. Some time ago I bought a pack of knurled head screws for adjusting the secondary mirror on my Dob and had a couple left over so I tried one and it works perfectly. The second one was used to help retain the diagonal in my refractor as the eyepiece retaining ring is hard to tighten, this also works perfectly. Hope this is of interest to anyone who might be having similar problems.