Good point. on the other hand I don't know how a front impact on the roof line compares to the loads in a roll (but I guess a roll at speed also has a strong horizontal force on the roof). What I remember from studies I saw in the past is that features like sunroofs make some difference. But the "we as lay people don't necessarily know", and intuition going wrong on other scenarios, was why I asked if there is a good source on that.