Factory made sliding sunroofs. They had a good bit of bracong welded in. This car is a crumple zonesstem. One of the first after the volvos. It has a good bit of flex. I would not reccomend cutting the roof without good welded in bracing. Ray
I have a Britax folding roof on my Variant. It was installed by the previous (German) owner and got approved by TÜV (like the MOT in UK). It does cut a hole of about a square meter in the roof, but I think the car's construction is so strong it can easily have it.
Jan Peter