I have the same setup, except I used a 5 gal. reservoir.
Float bucket doesn't have to be as large. I used this mini float valve, it works great:
http://www.usplastic.com/catalog/ite...er=23174#23174
Take your time setting the float valve so that you get the water level right. If it's too high it will swamp the bucket, too low (below your net pot) and the plants will thirst. Using a reservoir & float bucket you really dont' need an overflow hole.