I thought about a short rail, to have it more modular, but not a lot of "flat" space up around the dash.Ok Wow i like that a lot - but question, what about throwing in a whole Ram compatible rail somewhere up there? So that it can support more mounts. This is a great design though and might steal this as my starting place.
And I personally dont like to:
-use double sided tapes to hold something down that may have a "decent" amount of weight on it (phones, tablets, radio, etc). Especially where I live (just outside Sacramento, California) we get 110+ summer days and upper 20 degree winters. So in the summer, the inside of the car, especially dash, will get hot making adhesive more likely to fail over time.
-I try to not cover any vents/controls/knobs/screens as much as possible.
Those are just personal "guidelines" I stick to for myself.