Hydrocars,
Bob's plate size is 6" by 6" by 1/8" of either 316L (I Read) or 317L (I heard him say on the video from Smack on the Booster Run)
Last I heard he was planning a 6 X 9 Plate size but I don't know if he has proceeded that far yet.
It will be interesting to see what his larger size will produce in liters per minutes........