product-specific shipping restriction

I need the ability to flag shipping restrictions by product, eg, "this product can't go second-day air". Ideally, this includes the notion of "can ship by air if customer agrees to hazmat surcharge", but that can wait.

As luck would have it, I'm a developer who supports the GPL -- what I'm missing is the required knowledge of ZenCart's inner workings. It looks like similar problems have already been solved by the available shipping modules; I'm hoping that someone can point me in the right direction so I can skip over part of the learning curve...

tnx!

Product shipping restrictions can get very complicated and become most complex when mixing and matching products, shipping methods, etc.

While this is not impossible to write ... as in you could even make products shipping module oriented as well ... you need to really break down what happens when ...

What Shipping method is being used?

UPS? USPS? Something else?

Product A cannot go 2nd Day
Product B can go 2nd Day

What happens when Product A is in the cart?

What happens when Product B is in the cart?

What happens when Product A is in the cart and Product B is in the cart?

Is there a 3rd or 4th possibility?