BHertz

I have a 2006 T&C Touring equipped with the stow & go seats. The owners manual states that it must have a mini spare tire as a full sized spare may damage the vehicle. With the stow and go seats the spare is mounted below the driver and passenger seats.
I have taken measurements of the mini spare and the cover that goes over it and it measures larger than the full sized spare on my 98 Grand Voyager both in depth and diameter.
Does anyone have any knowledge as to why Chrysler will only recommend the mini spare??