Yes, all Porsche factory cars for school are fitted with the foldable buckets.
Personally, The foldable buckets are completely usable with only a 3 point belt, the base, as in where I seated in, hugs my bottom perfectly, I do not slide around in it. The shoulder 'wing' are wider in the foldable bucket, I would prefer them to be a bit tighter for support. Personal taste. Seat back angle leaves plenty of room for helmets.
The 918 style seat. In the 918 they are installed in a more upright position, feels bad for street driving but perfect on track, as the elbow angle is basically 90 degree, perfect leverage for steering.
Same seat installed in a 911 have a bit more reline built in, quite a bit more comfortable for street driving and and that extra angle is enough for me to feel comfortable even with a helmet on.
The base is a bit wider than the foldable bucket, my ass is not big enough to fill it completely, not an issue in the 918 with the 6 point harness, but with only a 3 point seatbelt my ass would slide side to side and front to back in it. Learnt that the hard way when I track my 911R, as I don't have the luxury of using my left leg to brace like I can in a GT3RS.
The shoulder 'wing' is tighter in the LWB, personally I prefer that for lateral support.
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