I agree with that assessment. I did go a step further and mount my y-axis rails directly to a squared surface for my aluminum milling machine to prevent flex of any kind. But it is a much smaller machine so this may not be practical for you. This mod also reduces z-clearance to just over 1/2" (but I didn’t think I would be milling metals over a half inch).
Problem is, this machine is so superior to my 1000mm x-carve that now I am working on taller plates to hold the gantry so I can mill up to 1.5" thick. Hopefully this will not compromise rigidity. .25" aluminum is on order for this mod:
Notice the x-axis makerslides and the stepper mount are now centered - hopefully that will gain some rigidity by reducing the angle of force applied by the router (shorter lever arm).