[ClausGraf]

I also made a pair of adjustable braces. However I found that in my case, I need to make a short adjustable brace (between the car floor and the bottom of the dashboard structure) to push it up slightly and keep the door mounting surfaces (where you bolt the door) vertical.
The section of the floor where I put this short brace was supported underneath by the wood frame I built.

Regards

Claus