Thanks for your help, I've looked in the data.ini and it seems to be ok :
data.ini for TANK_170F104NATO :
[WeaponData001]
TypeName=TANK_170F104NATO
FullName=170-gal Tank NATO
ModelName=TANK_170F104NATO
Mass=605.559998
Diameter=0.475000
Length=5.572000
SubsonicDragCoeff=0.200000
SupersonicDragCoeff=0.770000
AttachmentType=
SpecificStationCode=
NationName=
StartYear=0
EndYear=0
Availability=0
BaseQuantity=0
Exported=FALSE
ExportStartYear=0
ExportEndYear=0
ExportAvailability=0
WeaponDataType=5
MaxFuelAmount=501.230011
Asymmetrical=TRUE
RightModelName=TANK_170F104NATOR
and for TANK_170F104NATOR
[WeaponData001]
TypeName=TANK_170F104NATO
FullName=170-gal Tank NATO
ModelName=TANK_170F104NATOR
Mass=605.559998
Diameter=0.475000
Length=5.572000
SubsonicDragCoeff=0.200000
SupersonicDragCoeff=0.770000
AttachmentType=
SpecificStationCode=
NationName=
StartYear=0
EndYear=0
Availability=0
BaseQuantity=0
Exported=FALSE
ExportStartYear=0
ExportEndYear=0
ExportAvailability=0
WeaponDataType=5
MaxFuelAmount=501.230011
Asymmetrical=TRUE
There is certainly a little something to do, but I don't know what......
Ludo