"Seat" is a gmt object that is positioned with something like 3DsMax, ZModeller or 3DSimEd. Adjustments of the seat object are made in the vehicle's "car" file. Look in the "Team" folder (i.e. GTR2\GameData\Teams\GT\Ferrari 550 Teams\BMS Scuderia Italia) and then open the "car" file (i.e. 03022_GT_Ferrari_F550.car) using Notepad, Notepad+, WordPad, etc.and then locate this section:
Eyepoint=(0.363, 0.59, 0.345)
CameraTarget=(0.000, 0.550, 0.15)
MaxSeatRear=0.06
MaxSeatFront=-0.01
MaxSeatUp=0.01
MaxSeatDown=-0.01
FrontWheelsInCockpit=0
SteeringWheelAxis=(0.0,0.1736,0.9848)
SteeringWheelType=5
ExternalDriverPosition=(0.398, -0.24, 0.2415)
FirstPersonDriverPosition=(0.36, -0.389, 0.171)
LeftSideSteering=1
ShiftStickPosition=(0.06, 0.315, -0.06)
In this example bold & italicized text are where the seat position is dictated.
* BE SURE TO BACK UP THE CAR FILE BEFORE YOU MODIFY IT *