I've just seen this in the revisions to next year's Blue Book:
1.2.2. The ROPS must not unduly impede Driver and Co-Driver access to the vehicle. Members may intrudeinto the interior space by passing through the dashboard, front sidetrim, rear side trim, and rear seats which may be folded down. ROPSmust not extend beyond the front upper or rear suspension mounting points of the vehicle, with the exception of backstays which may extend beyond the rear suspension mounting points if necessary to achieve the required 30° angle
New bit in red. So that addresses a long standing problem with backstays and the 'unique' 2CV suspension arrangement.
That's good news. Good spot.