I was also going to mention that a medium pizza box fits, too! [/QUOTE
I know this is in the 07+ section, but on my 04 I have fit (2) 16" pizza'a plus (2)- 12" pizza's under the seat. With one more 12" in front of me wedged between the seat and the glove box. I don't recommend the 5th pizza, but long story.. Oh yeah, my wife and I were riding 2 up also
Here's a humorous storage video on a 650. I think this is where I got the idea I could pick up pizza on my 400.