Quote Originally Posted by JAZZCNC View Post

The C section inner surfaces won't be flat so will need milling for the rails. Then you have the problem of making sure the uprights are perfectly parallel in 2 planes and perfectly perpendicular in the other.!! . . 99.9999999% Nailed on that you won't be able to weld this up and keep parallel/perpendicular in all planes.

I feel If you go with this design you'll regret it come setting up time.!
This is so important when developing your design. I don't know how much experience you have welding? But things will distort and if you are just starting out you want to be able to weld in a flat position as much as possible. Building in adjustment is key - especially if building using limited equipment and skill. You can draw to crazy levels of accuracy but when it comes to drilling a hole or cutting to 0.1mm using the kit you have in your garage!???

With my cheap drill press, cut off saw and stick welder I have needed some tolerance building my frame and I have seriously taken my time!!!

You are doing the right thing sharing on here though you will get some v helpful advise.