When it comes to fitting a harness, you need to take extreme care in positioning the fixing points. You not only need to ensure the harness is fitted to an adequately strong area of the car, but also need to consider the route the harness straps too.
There are actually guidelines and fitting instructions available from most harness manufacturers to ensure they are fitted correctly. Fitting a harness incorrectly is incredibly dangerous so if you have any doubts at all speak to someone in the know before you start.
As a rule of thumb the harness straps need to be kept as straight as possible. Starting with the shoulder straps, imagine drawing a horizontal line off the driver’s shoulders. The operating angle of the shoulder straps is anywhere from this horizontal line to 40degs below. So, bolting the harnesses into the floor immediately behind the driver’s seat is no good.
As for the lap straps, imagine drawing a line downward to the floor from the driver’s spine. The lap straps should be fixed approximately 45degs towards the rear from this imaginary line.
If you don’t fix the harnesses in these correct positions you run the risk of serious injury in the event of an accident, so take care to follow these instructions.