I'm trying to set up a replacement cart for my company's site. Their shipping, however, is a little strange...

Basically, I need to set it up so that if the customer buys a product from Category A, shipping is $12.95. If they buy from Category B, it's $9.95. However, the rate is a flat fee; that is, no matter how many products they buy, the shipping price stays the same. Also, if they buy a product from Category A and B, they get charged the shipping rate of A.

I thought about using weights to set up the different rates, but that adds a shipping charge for every product. I've also looked up cloning the flat rate module, but I don't think that would handle the "A+B=12.95" rule (although I could very well be wrong, since I'm new to Zen Cart and shopping carts in general).

Does anyone have any ideas about how I could get this set up?