West Coast Green: if you're using the larger size five gallon buckets instead of the smaller two gallon or three and a half gallon ones, why do you want the unnecessary complication of a reservoir? I could see it with the smaller buckets. I would think a simplified version with individual buckets, self contained and vigorously fed with large air stones supplied from a single pump of sufficient CFM's would be a lot easier to control. For one thing, if something goes wrong with one of your plants below ground level it's not as likely to affect the others.
I've been working with five gallon bubble buckets and ten gallon bubble tubs, (a knockoff of Stealth Hydro's unit), for about the last year now and I really like the buckets better. For a single well established plant I really don't think you can beat them for their simplicity. Admittedly, the 3 1/2 gallon size are a little easier to handle but that slightly smaller volume requires a little more care. I have a friend who had a set up similar to what you're planing; of aireated buckets connected to a reservoir and he still had his share of problems with controllers, leaks etc. And when he had a nutes problem in one bucket it spread like the flu to the others. HSA