Hey, I did this when I bought my Roadster last November. When you remove #15 the tire just fits in there. There is also already a place for the tools and jack in the foam that is already in the car, I think. You don't actually have to buy #14 unless you really want it. It all works well without it. I just bought the tire and tools from ebay. You do need the screw clamp that holds the tire in place though.
There are some pics here...
Want Spare tire kit pics
Also, instead of the foam (#14), I put the compressor and fix-a-flat that came with the car inside the spare.