I'd be worried too about anything suction cupped to the outside of a moving vehicle! Suction cupped to the inside with a little 'Hearsy Kiss' type magmount antenna would keep everything dry, no worries about water intrusion. Plus, the antenna would be mounted vertical atop a good ground plane, vs a lossy rubber duck at an angle.
I had to relocate my GPS for aircraft use, the AIO would lean against the side window... resting on a window sill. One small suction cup with a small hole on the attachment side for the antenna (non OEM) kept it against the window. The GPS unit would be looking at the horizon or lower. I removed it from the circuit board and mounted it 90 degrees to the circuit board, facing up. Plus, my case was a metal case so it had to be cut for the GPS antenna to 'see' the sky. See my photo's KA1GJU-6 73 de Kriss
