Harness anchorage points

[Johno]

Need some advice on this topic.
I know most people are mounting their top anchorage point for their harness off their roll bar tube but I plan to mount mine from the top of the seat rail box section the same height as the mounting plate for the roll bar base plates.
Iv'e tried to keep my seat as low as possible and the distance from the the seat base to the top rail is more than the 450mm as specified in the IVA manual.
The area I'm struggling with is this... I'm using a GRP seat with holes through the top for the harness. Correct me if I'm wrong but as long as the harness does not pull down on the seat (this then becomes a load bearing structure) this will be OK but on a post somewhere I've read "as long as the anchorage point is not lower than shoulder heigth it will be fine".
So what if the examiner is a different height to me and the top anchorage point is either above or below shoulder height without touching the seat which is acceptable....
I plan to make machined spacers if required to clear the seat and use eye bolts as Westfield.

Sorry not very good at explaining myself but I hope you get the jist...