Need 6' x 4' bed, 4 axis router design.. Help..!

[Jonathan]

In your equation R is fixed at 16mm and r varies from 0 to 10mm (in this example). So R^4 - r^4 gets smaller, and the inertia goes down.

Yes, of course. I was tying to compare like with like stiffness not diameter since I was assuming you'd use a bigger screw to compensate.