[bearcat44]

You wouldn't need 1 1/2 or 2" pipe. 3/4 or 1" schedule 40# would be plenty strong. #3 10' pieces, #4 90 degree elbows, #6 T's, #6 90 degree street elbows. Take two of the 10 footers cut them to 6' or what ever length you like, the amount left over cuts to the length for the ends. The six T's are equally spaced three to a side facing down, the six street elbows then allow you to connect three supports and inch or two below the top of the sides, drop in your plywood, and set your mattress on top.