Very cool Rawhide, nice picture! Are you having fun yet? I was always afraid of the milk crates since I use a variety of bottles, thinking they might slip out. Dude, your awesome!
I use foam packing sheets between the layers of bottles. You can get 100 sheets off Ebay for $6.99 plus 4.99 shipping. They are 12x12x 1/32. I tear them into thirds and they work great and if you divide the total by 300 its' only .03 cents apiece. The ebay item is #260547251164. Hope that this helps you.