I just spent the last two weeks putting this together. Framing is 6' x6', made out of 3" 3/16(7ga.) tubing. The two Y axis ballscrews are 16mm. The X axis is a 25mm ballscrew. Z axis is a 16mm ball screw. Both Y axis and X axis are driven with Nema23 570oz. motors. And the Z axis is a Nema34 1200oz. motor. I made all of the mounts to be adjustable, in case I needed to later go to larger size motors. But there doesn't appear to be a problem with the Nema23 motors for X/Y.
I'm using Mach3 with a C10 BoB, and an Ethernet smooth Stepper card. I use Fusion360 for CAD/CAM.