The wood block I have is made from three pieces of wood. The bottom
piece is 5/8" plywood appriximately 8 x 8". I then have two pieces
of wood cut to the proper thickness and placed on the outside edges
so that when jacked from the bottom, the hull is supported in three
places, the two outside edges and the center. This prevents any
punching of holes and also tipping. The jack I use is a small
hydraulic jack that I place on the trailer. After the first use,
the bottom piece of wood has a nice notch in it for future reference.