Don- I think it's actually a 16x20 inch maximum, on the baseboard.
Eddie, I beg to differ with you. I make 20X24.s on the base board of my Saunders/LPL 4550 XLG routinely and I use a Saunders 4 blade adjustable easel to do them. And it fits on the base board. A bit tight, but it fits. Don