Optimum Bed Tower Height?

It seems to me that the most useful bed tower would be high enough to provide a level surface with a cab mounted rack. You've seen pictures of Tacos with camper shells that have a rack mounted on them. They extend cab's rack almost the length of the vehicle minus the engine hood. What is the most useful height?

 

I think you answered your own question.

Although, I see guys running the mid height racks so their RTT's basically end up the same height as the cab when mounted.

 

I like lower profile for a few reasons - lower drag on the highway, I can fit my truck in my garage with the RTT installed, not as far to fall from my RTT when I'm drunk and easier to lift my dogs in.

For me - the height of the CBI rack is perfect at about 14.5" above the bed rail it puts the top of the RTT slightly above cab height

 

I've wondered this same thing. If I ran a rack I'd like to have my Kayak or Board at the same level as my factory roof rack, but I can't seem to find one.