Detatiled shipping

Im looking for a detailed way of shipping...
My store sells items that are all pretty much the same size, but Im gett nailed on shipping on the larger items (internationally)
I have 4 sizes
size a - 16x16x4 weighing 1#
size b - 18x18x6 weighing 1.5#
size c - 20x20x6 weiging 2#
Size d - can be set as size A

the issue is when mulitple items are shipped.

1-3 As = first class international
4 As 24x16x12 4# 15oz
2 sizes Bs will fit in a 20x16x12 box weighing 4#
2 size Ds will fit in an 18x18x12 box weighing 5#

any odd number B or C needs to be shipped as 20x16x12 + 18x18x6 (ie 3 items would be one of each) currently OC assumes the size is my default size, and just adds weight.

are there any modules I can configure, or anyone want to shoot me a prince on writing a module/vqmod for this?

Normally we would run weight based but the larger sized items (b/c) are bulky and shipping is outrageous on them.

I'm not sure exactly what your rates cost, but can you just use the total volume in the cart to determine the shipping price? If so, Volume-Based Shipping would work for you. That can determine the price based on both volume and weight, which it seems like should work for your products.

I have just responded to your e-mail, so feel free to continue the discussion there, as I check my e-mail more than I check the forums.