I set up a system very similar to yours 2 years ago, but I used Alaska Grow Buckets (
http://www.alaskagrowbuckets.com/). I used a float valve and had very good success. The Alaska Grow Buckets (AGB) allow for much more root space as well as air.
There's some pics of my set up on this thread.
http://www.tomatoville.com/showthread.php?t=30435