Wow, and I thought I over engineered stuff. If you have access to a mill and can make that then you should be able to make something that flows with the rig better than a block and square tube. If you are going to pay a shop to build it you might find something off the shelf that is more cost effective. My rates for machine work are $ 125 an hour, those blocks would cost more than the rack its self. And if you have a decent roof rack you wont need cross bars, it can go directly to the stanchion and you can keep the profile even lower... jmho