Matching roof rack height with camper rack

How does one go about matching a cabin roof rack to match an existing camper rack?

Currently, the Yakima Jetstream sitting on an adapter for the Leer roof rail allows for putting on the existing cargo box (as shown), SUP racks, etc.

What would need to be done to add rails (preferably the same system), to match the height for the anticipation of adding a larger RTT (hard versions seem appealing) spanning over the camper and cab?


What are the issues with leakage and how is it preventable (esp. in the PNW)? Thanks!

 

I've heard of people using spacers between the roof and roof rack. My Prinsu rack comes with spacers and they can be switched out for larger spacers.