Nutrient solution volume and nice containers.

I've designed a RDWC system and am ironing out the details. My previous DWC grow used 6 gallons of solution in a 10-12 gallon storage tub in a 2'X2' area. That worked out pretty well but I fell like more height and less base would be a better shape. Buckets only seem to go to 7 gallon. Rubbermaid makes a 10 gallon brute can, but it's a little short/squat. The 10 gallon water coolers look pretty sweet but are expensive (I plan to insulate the buckets though) and might prove difficult to modify reliably.

So 6 gallons, is that the ideal water volume per plant if plants are getting 4 square feet of light?

And does anyone know of any nice sized containers that would hold that ammount plus a little extra for the net pot?

I only remember seeing 3 and 5 gallon buckets at the garden shop, so I'm seriously perplexed on what containers to upgrade to. If I can't think of anything I will probably end up using the storage tubs again.

I think the 7 gallon buckets might end up working well. Since I will have a reservoir and each bucket will hold 5.5 gallons of solution to 1 inch below the pot, that's 22 gallons, or 7.33 gallons per plant.

Is there such a thing as too much solution? Could you run longer times between changeouts with larger solution volumes?

walmart has a 15gal tuffbox that is great for single plant dwc. very strong and cheap, around $11