Columbia Seat Limitation

http://www.faa.gov/data_statistics/a...a/B_0904_N.txt

Prayers go out to the family. Horrible, horrible accident.

As a family man, the incident caught my attention. Particularly the six
people in a Columbia part. Sadly, children were involved but with 4 adults
and 2 children (according to various sources), W&B was at best borderline.
Other forums have mentioned that there's a limit of 4 passengers in the
Columbia regardless of size. Is this true? Are the limitations
model-dependent or is it a FAR 23 thing? Seems to me that seat belt
requirements may drive some of this.

Marco