The rear bolts in my sedan, the outers are on the wheel tubs
I am assuming that you run the belts up inbetween the seat and the wheel tubs? I am guessing that you would need to have the mount low down nearly at the floor to ensure that only the belt is visible?
and the two inner mount points are just either side of the tunnel.
I thought that from Jack's description it would make sense to have the rears in basically the same location in relation to the fronts
The upper mounts are on the parcel shelf, but I have seen them fitted to the C pillar.
I assumed that they would go on the parcel shelf, again I am assuming that they would be close to the "C" pillar, given that you have seen some that have mounted them to the "C" Pillar.
The other thing that I need to know is there a standard seat belt bolt, if so what is the pitch and diameter of the thread?