Corey,
I was only repeating what Chris tod me when I spoke to him at the Columbia Repticon last July. I agree that a rack out of 1/2 inch XPVC for a width of 3 V-18 tubs shouldn't be a problem. I too had thought about using extra supports for a rack that was capable of 2 short V-35 tubs or 4 V-18 tubs per shelf. I think it will work great for you. I was talking about what could be bought readily built so that there would be no additional cost for a custom build. Let us know how your custom rack turns out, I look forward to some pictures. Based on the pictures of the other stuff you built, I'm sure it will come out looking good.