Difficult to say.

On my current build both red and violet distances are around 350mm and even without 3rd gantry profile and 3rd rail on z all looks like it will reap aluminum like butter , i would say steel will not be a problem at all with small cutters.

So in your case for me it seems logical to extend the red distance a bit. Though the third rail a kind of compensates for that.

I second the previous advice given to you. Make sure piece by piece its possible to fix all together and align it/ tram it/ . Its a complex assembly so dry test all in software.