Daher-Socata TBM 900 Pilot's Information Manual page 327

PILOT'S OPERATING HANDBOOK
ONLY zone B and zone C can be modified for seat configurations.
Location
number
1) Configuration 6 seats standard=Basic Index and Basic Empty Weight
2) Configuration Modified=Basic Index Modified and Empty Weight Modified
1 Mid Seat is equal to 1.7 point of Index and 37.47 lbs (17 Kg)
1 Rear Seat is equal to 6 points of Index and 52.91 lbs (24 Kg)
Remove or add the number of index point for each item removed or added.
Remove or add the weight for each item removed or added.
3) From the new empty weight and new basic index, perform the weight and balance graph.
Edition 0 -- October 31, 2013
Rev. 1
For all configurations, verify that your luggages
are stowed and attached in the appropriate areas
Fwd baggage zone
Pilot zone: No modification allowed
1 Mid Seat = 1.7 point of Index
1 Rear Seat = 6 points of Index
Cargo zone
SECTION 6
WEIGHT AND BALANCE
Page 6.4.3