Doesn't stay stuck? This worked for me.

I had problems both with the mount not staying stuck to my dash, and with the suction cup not staying stuck to the dash mount.  It's a combination of temperature fluctuations, a textured dash, and the weight of my phone. 

My solution was to buy heavy duty velcro intended for outdoors (like to fasten things to brick).  I stuck one side on the dash and the other on the bottom of the dash mount and let those set overnight without putting them together.  I then velcro'd them together.  That solved the first problem.  I then used the a second set of the same heavy duty outdoor velcro and stuck one part to the top of the car mount (now velcro'd to the dash), and the other part to the bottom of the suction cup (since the weight of my phone often caused the suction cup to come off, especially with temperature fluctuations).  I let those set overnight as well before connecting them.  Now I've got it all together and it never comes apart.  If I needed to remove the entire unit, it's just a matter of the bottom velcro that's stuck to the dash - and a solvent will help clear that up.  Hope this helps.