I knew I had forgotten something!
Only for drivers who use the full face helmet you need to add these lines in the ext_config file (Unfortunately impossible to upload the complete .ini file)
Sorry!
[DRIVER3D_MODEL]
NAME=Driver_Ferrari_1979
POSITION=1.1,1.1,1.1
[DRIVER3D_HIDE_OBJECT_0]
NAME=DRIVER:Casco_70:WCEXTRA2
[DRIVER3D_HIDE_OBJECT_1]
NAME=DRIVER:Casco_70:_312T4_FACE
[DRIVER3D_HIDE_OBJECT_2]
NAME=DRIVER:Casco_70:WCHELMET