I use the stick on mounts gopro sells.
I have 1 on the front bumper, 1 on the dash, 1 under the hood, and 1 in the cluster.
The bumper 1 has been on the truck with gopro doing over 100 and taken a few hits.
I used 1 of these on my toolbox with 3m RED double sided tape on the bottom. Its been there for years, but the toolbox is now in my attic.
https://www.amazon.com/gp/product/B00HRSBTNA/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
I have not used any suction cup mounts cept 1 time on the INSIDE of the window.
If Im worried, Ill run a cheap ass fishing leader thru the steel pivot piece of the case (under the door) and then loop it around a secure part of the truck, or tack it down with something else.
I once pulled the camera off and forgot to undo the leader, the camera snapped right back outta my hand and stayed on the truck.