No worries mate, if I have anything that could help you out I'd be more than happy to share!
The drawing above is not to scale, it was merely to send to MSNZ (the New Zealand governing body for motorsports) to get sign-off on the design.
I will most likely add a harness bar and forward bars at some stage in the future, in order to compete at the track, but initially I just wanted a street car/track day car with diagonal belts.
The diagonals would be the bars in the way for back seat passengers, but they are required by MSNZ regulations (well, at least one is).
And in NZ you can't have back seat passengers if you have roll protection in the car anyway...
But by my thinking and having played with the PVC pipe mockup I made, the rollbar should be easily removable. The front seats would have to removed but they come out easy enough, and aren't heavy.
Having the backstays bolt to the parcel tray is the key (obviously a brace underneath would have to be added, such as the one I've put in my car).