Comments about Bogen Imaging Bogen - Manfrotto Rapid Connect Mounting Plate, 4" x 4" for 3057 (Spare), 3038, 3039, 3047, 3055 and 3063 (#3297):
I use the 4x4 plate to attach gator board easels to my tripod for doing watercolors. I don't think you can buy a better, more stable and versatile system. Of course one does have to attach the plate to the gator board, I glue pieces of heavy gator board to 6 inch squares of plywood with a [$] flange nut glued in to attach to the 4x4 plate. Make spares in any size, you only need one plate.