This is the design for the top plates I have used for my concrete piers. Works beautifully and have had these plates on several as I have move from place to place. Have used it to mount an LX200 with wedge as well as an EQ6 - its very adaptable. On the inferior plate for the holes which accept the pier bolts, I cut them into small arched slots so that there would be some additional adjustment for N/S alignment.
http://spazioinwind.libero.it/gpasi/tech/pier/pier.htm
http://spazioinwind.libero.it/gpasi/...ier/plates.htm
I can post some photos of it as I've just made a new pier and deck in preparation for a Sirius observatory