Tam - when I first sought information on how best to compose a container mix, I found this thread on Gardenweb:
http://forums2.gardenweb.com/forums/...615891.html?70
Tapla (Al) is a Master Gardener and his thoughts on container gardening are very instructional. I think you'll find it useful. I don't frequent GW very often, but I keep a printed copy of this thread in my garden journal so I can refer back to it periodically.