Is soldering an option?
Soldering will cause magnets to lose magnetism. I have considered
doing what you are thinking about and my idea is to use a crimper,
it has a hole in the middle and when you squeeze the handles
together, four small teeth come out of the hole on the 4 quadrants
and poke a dimple into the tube. If you do it gently, it should not
interfere with the other magnet getting close enough to hold and
should just hold the magnet in place in the crimped tube. I got the
first crimper at Boeing Surplus in Seattle (now closed, I think) and
have gotten another on Ebay in the electronics section.
Donna in VA