I just got some of these and put one in each car. I do plan on checking on a regular interval. The nice thing with these is the bucket collects the moisture.
A week in and I'm already seeing a difference.
Alan
Classic Industries has multiple options.
I went with these as I already had the speakers
https://www.classicindustries.com/product/1967/plymouth/barracuda/parts/ma819102.html
Alan
I use SketchUp, not quite a "CAD" tool but you can do some detailed stuff.
Before I retired I used MicroStation a true CAD program. Nothing free about it.
Alan
I get it but what about passenger phones, I'm not saying you need to regulate passengers but how are they to know if a phone belongs to the driver or a passenger?
Alan