Steel x axis idea

Hi all
Just expirementing with different ideas,did someone ever build something like this,I know wiremonkey experemented with stiffening c beam with steel tube(how did that ended btw?) but this is not wor stiffening purposes,more to clear ballscrew and bringing spindle closer to x axis.
Idea is to cut open middle section of steel beam and weld half piece of 50X50 to clear ballscrew nut.I know joints are week points so 50X50 could be 3-4mm thick wich is I think more than enough.
Opinions are welcomed.
thanks

No increase in strength or rigidity for the introduction of distortion in cutting and welding in the insert? Why?
Start with a smaller box and weld on additional box sections to build your cross section, that will at least add some strength and rigidity with less chance of unacceptable distortion.

The other way to do that is start with the box section then weld 2 thick bars onto the front face, one at the top and one at the bottom. Leave enough gap in the middle to clear the ballnut. Rails can mount to these bars and you have plenty of depth for the threads. Similar outer profile to your drawing but without the discontinuities.