I tried the HANS in Mugello this week . Absolutely no problem when driving . 

When you are sitting at stand still you can easily hit the back head rest and '' think'' it will be annoying . But once you are driving the car, you do not touch the headrest ...or at least you do not feel any inconvenience . 

Again, there were at least 30 cars which had the LWB seats ( mix of GT3, GT3 RS and GT4 ) . Most people have a HANS . I did not hear anyone complain .   It probably does not fit to everyone , but that percentage is very very low . One must have an extremely straight torso/neck .  Or a very thick thorax which would keep the HANS back when buckled in . 

Here is a photos to show you at standstill : ( click to enlarge )

IMG_1975.jpg


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 964 Carrera 4 --  997.2 C2S , -20mm --  991 GT3 RS