[This is a tangent that started in the recent thread about special orders.]
Well, I purchased this spare tire holder, part #31399083. It consists of a large styro cradle for the tire, a styro wheel insert to secure the tire and hold the jack & ancillary stuff, and a new floor panel. It also includes a bag for a dirty punctured tire and work gloves, a nice touch. I doubt the whole package came to ten pounds.
And I will be returning it. While I expected the new main floor section to be higher than the old one, never did I expect it to be as high as the top of the spare tire when it sits on the original floor. I anticipated gaining a little vertical space in the middle of the trunk and losing some vertical space in the rest of the middle area for a net gain of usable space, but that's not the case. Unless you only carry a briefcase and two-suiter in your trunk and value neatness, I do not recommend this item.