EDIT: experimented, can't use free shipping code and 15% off code at same time, which is fine, how much can you expect. It's a great deal with the 15% off. Thinking about the Hotchkiss leafs and some other big items I need.
I tried that too! But still, the 15% was nice because I was going to do an order anyway! If you buy enough stuff they will send you Summit Bucks and discount codes. I bought some slicks and got $30 in Bucks and $20/off $100 purchase code.