In article .com,
Paul kgyy wrote:

I've used a suction cup mount for several years, and it mostly works
fine.
However, it has fallen off a couple of times. I would hate for that
to happen in the middle of an ifr approach so am looking for an
alternative.

As long as you keep it wet, it will stay in place.
On a hot day, it may be possible for the water between the window and
the suction cup may evaporate.