The largest s/h pots i use are 10" dia & about 9" high, these are glazed pots with no drain holes.
I just drill 2 holes close together.Pretty easy with a carbide tipped drill.Just put some tape in the place where you want to drill other wise the drill slips around.This type of pot goes upto 14" dia so i,ve got a little growing space.
I have the res height a little lower for these bigger pots(about 3/4" high) because there is still a large amount of water in the res.