Got a bit more done this past while
The GD body has threaded inserts moulded into the body and the centres of these inserts need to be transferred onto the legs so some reading done and some lengths of steel flat - drilling them for the screen fixing bolts, screwing them to some blocks of wood and bonding the blocks of wood to the inside of the body also made up some spacers that were the same diameter as the post legs from the carbon cut from building the dash. Thanks STR for the tip :)
The screen needs to be 6mm of the bulkhead at the posts on either side and also 930mm from the curve on the rear bulkhead to the top of the screen (inside measurement at top of screen)
Pictures speak 1000 words at times so some pics.