Finally there seems to be a number of adjustable mounts available,
from RAM, etc. Seems like a 3" to 4" overall length would be good

I've used the RAM mounts for my GPS and Radio. They are Great. The biggest
advantage is if you are sharing ships and each person has their own "gadget",
you leave the Ball Mounted permanently in the ship and everyone just attaches
their particular "gadget" when they fly and takes it with them when they go!

Douglas