Making an extrusion roof rack for my smartcap, but looking for ideas on what to use for the feet

I am building a rack for the Smartcap, and I can mount it directly to the T slot rails using L brackets, but looking at other ideas since I want to raise it a bit as its wider than the top and I want windows to open fully (side windows).

I am looking at ideas on that to use for feet. Preferably looking a a "C" shape so rack can be bolted on top of the feet, while the lower part gets bolted to the rails

 

A good source for extrusions.
https://8020.net/

 

Two L's can become one C pretty easily.

 

I built a bedrack recently and mounted it to my Diamondback cover. Had the feet done by sendcutsend in .25” stainless. You can design it online and they do the rest.