Go to Hobby Lobby or any craft store, maybe even Wally World and pick up some suction cups with the hooks on them. I use the small ones. The hooks go through the holes on the plate and then the suction cups stick to the windshield. I have mine in the lower passenger corner and it does not interfere with sight seeing.
I also purchase blank plates from Kiley Mold Company and the ladder brackets. Neat application. I believe I paid $12 for a pair of blank plates.
Here is my Original Post
in this thread.