ABS is okay but it has some flex and these are long prints so warping is an issue (for me anyway). I used PETG for the flexing parts like corner pieces and clamps and initially used it on the center assembly. I couldn’t get it to square up at all though so redid the center in the new 525 design with PLA for ultimate rigidity. Perfect square right on installation! I made a few parts in ABS but some cracked with fastening.
Originally mine was 38 x 38 but I shrunk it down a couple inches each side so I can put handles on the board to make moving it easier.