Some good progress there Mr-P
Looks like you have been cracking on a bit since your last post
The examiner that tested Ash's car wanted to see either the back stays welded or fixed by two bolts per stay.
I don't know if the Exeter IVA station would be of the same view .... At your stage of the build , it wouldn't hurt to put in some extra fixings to be on the safe side
I was having a read of the IVA manual the other day .... There is a minimum height for the roll bar cross stay ( If harnesses are going to be mounted on it ).
This height is taken from a reference point on the lower seat squab. 400mm above the datum point springs to mind but I would check the manual first .... My brain aint as good as it used to be
Well done on your progress.