When I go to Las Vegas and then swing by Buttonwillow Raceway Park for a weekend event on the way back, I can get the following in the trunk area and still clearly see out all the back window.

1. 10x10 Canvas Canopy with support frame.
2. Medium STR6 bag with my Driving gear in it (Gloves, Suit, Shoes and Helmet)
3. Both additional SRT6 bags with basics for a week trip (clothing, toiletries, etc.)
4. A dual folding chair from Jegs.
5. Camera mount with Straps.
6. (2) large magnetic signs that have my track numbers and stickers on them.
7. (2) medium to heavy wind breaker type jackets/coats.
8. A bag or two of snacks and assorted drinks (water, ice tea, etc.)

It IS a bit of a puzzle, but it fits nice and snug. You should have seen it on our way out to Christmas of 2006... I couldn't even see out the rear window on the way there with all the presents in the back.

Quite a lot of room as long as you take into account that the widest section near the fuel tank/back wall of the front cabin is just under four feet wide. The other obsticle is the shape of the rear hatch...

Cheers!