SG always have a spare sticky pad in the box, both for the camera and the GPS antenna, if you run out just hit up Jon that run SG in the states and he will have a few spares going out to you..
The plastic mount itself you can of course reuse the camera should also come with 2 of them, a thick one and a thin one, i have done this several times donating my old cameras to people i care about, but the sticky pad thats a 1 shot deal.
Regarding aim it is a bit silly to have parts of your dashboard in the frame, as nothing happen there, but you could also say the same about what extra sky you will have in frame if you aim dashcam too high.
As jokiin say it is a matter of the light metering of the camera, so if it is aimed too high it will adjust its settings for the lots of bright sky, and then you can have scenarios where the road level can be underexposed, and really it is what go on at / on the road that are of interest for a dashcam.