So we tried it out. Using two imperial units of mass - the Barry and the Sandbag.

Barry's report on the experiment:
With the assistance of one of my workshop neighbours we measured, using a digital vernier, the door gap change just above door handle height.
I sat (feet dangling) on the rear slam panel with my sandbag in hand. This combination weighs in at 89kilos (72 for me, 17 for the bag). The centreline of the rear panel is around 125mm rearwards of the rear engine mount centreline, so we've gone quite a bit over the calculated weight. ...which you will remember was 80kg ish.

Results:
The total movement was .22 of a mm.
I have to say, when you lean on the rear slam of your car, you'd swear the rearmost brackets were still in. You just can't feel any notion of motion as one might say.

Conclusion:
It's always been Barry's practice to have the top door gaps a tiny bit tighter than the bottoms. They only ever go out at the top when loaded up with drivetrain, when well-used, etc. Apparently the official Porsche manual says that too.

So that's enough. The very small movement is taken care of by the usual procedure. No weightlifting action required at the painters.