Racing Harnesses and Mounting Points

That mounting is going to compress your spine in the event of an impact so please change it asap - pretty much anything else would be an improvement.

Two options come immediately to mind :
- anchor point on the bulkhead as you mentioned with a suitable spreader plate
- add a harness bar between the backstays of your roll hoop at a height so it's just below the top of your seats and attach the harness to that

Taking the back straps over the top of the substanital tube at just above seat back level which I assume is part of the roll hoop would be a vast improvement.

Yes, I wondered about that but it looks a bit high. +15/-45 deg for the shoulder straps is what I've always found quoted and going over that bit of the roll hoop looks like a lot more than +15. Still, would be a vast improvement as you say.

That's the diagram - so +10 not +15. I was close :-)

My other advice would be not to run standard seats with harnesses. With straps either side of the seat rest your prone to them pulling aprt on heavy impact.

No expert but I thought angle should be measured on shoulder height of the person being retained not the seat ?
slipngripross I think is also right if there are no mounting/centering holes holes in the seats belts can slip off the shoulders - you can cross the belts behind the seats to prevent this but has to be done in a measured way. Looking at your harness with two straps off a single one it looks like this is already kind of in place but talk to the suppliers for more info ?
Worth using some google-foo to look into it one I found helpfull:
www.speedhunters.com/2014/06/takata-ask-the-expert-answers/
Looking at your cross bar this would be taking some of the force but not all as this would be split between the mounting point and the bar depending on angles etc.
James