I set the subject for my question as succinct as possible, so that about sums things up. 
I have a website of photos, each with a size attribute. If a user orders more than one product, I'm looking for a way to quote shipping based on only the largest. So if a user orders an 8x12 photo and a 48x24 photo they're only charged for shipping on the 48x24.
There are three groups of photo sizes:
8x10, 8x12, 11x14, 12 x 18 are $3
16x20, 20x30 are $5
36x18, 48x24 are $10
I thought about using product classes, but I can't seem to find a way to set product classes based on attributes.
I should note that I'm not a developer, but can copy and paste php if necessary,
.
Thanks for reading.
Cheers,
-Chris
