I plan on a single row of seats, with a countertop and barstools behind the first row, due to space restrictions in the room i am putting it in. How much space should I have to do this? Would a 12 inch countertop be big enough? Do i need 18 or 24 inches of countertop? How much space from behind the countertop to the wall should one have? What do you think is the absolute minimum?