This should be sufficient for any bare tube. For a
tube inside an
enclosure, then you need to take a look at how the tube is mounted in
the enclosure. Some enclosures just have plastic mounting posts
holding the CRT in place. That's fine for the CRT sitting on a desk,
but not good when the whole thing is dropped 2 feet from the back of a
truck. In those cases, I suggest wadding packing inside the enclosure
to keep the CRT braced by more than just the mounting posts.
For your amusement:
http://www.tabajara-labs.com.br/hal/index.htm
This is what happens on the above situation, with photos :o)