The first year we had the car, I removed the spare and ..yes you can fit a lot of stuff in there. However, after reading that the tire is supposedly part of the crumple zone, I put it back in...where it's been the last 25,000 miles.To me, the reasoning makes sense. Anything which will provide a buffer to the gas tank is a good thing. While the tire may easily rupture in a rear end collision, there will be a layer of tire rubber at the back of the gas tank..at least up to a certain impact. I would also think it would add a little more rigidity to the rear end fiberglass crumpling.
As for limited packing with the spare tire in place, we drove to Nashville(900 miles from here)...gone for over a week...with everything in the RT/10 including helmets. You'd be amazed at how much you can get into the car with a little creativity. Helmets are great for underware and socks. The spare tire area(and under the tire)holds all cleaning materials and more(plug kit/2 cans of fix-a-flat). We had to send the goody bags back via a different method.
Steve