For both the 300M and the Santa Fe, Suzie is stuck, using her OEM suction cup, to the trim that wraps across the passenger side above the glove box, just to the right of the radio. I've heard a lot of whining about how the OEM cup doesn't work. I don't even use the stick-on gadget (don't want to mar the trim with the goo) and it holds perfectly well. The 300M is particularly ugly because it's a compound curve -- concave horizontally and convex vertically. In both cases, the mounting surface and the cup were assured to be absolutely positively SPOTLESS when mounting. I think that's the key in 99% of the cases for both trim and windshield mounting.
I'd thought to mount it on the windshield, but because the 300M sits low as it does with the severely raked windshield, it didn't work well for me there. Got used to it that way, and that's why it's on the trim on the Santa Fe as well.