I have the full length K9 roof rack. I do love the flat surface. While K9 has a lot of accessories to assist you in mounting and securing all your desired gear I had a few custom brackets made to achieve some of my desired results.
1. The front light bar brackets to mount below the rack surface
2. a bracket adapter to mount my awing in tighter and at the height I wanted.
I've mounted both an ikamper and a 23Zero RTT with same K9 low profile RTT mounts.
Currently I have on my K9 Rack:
1. ikamper mini
2. 2 Alu-Box boxes and their K9 mounts, (w 2 50W solar panels)
3. under rack table and table slides
4. left and right flood lights
5. front light bar
I've redesigned my rack configuration several times and have mounted a 100W solar panel, rotopax cans, 23Zero tent (queen sized).
Point is, its very flexible.