I fitted xj-s coupe seats to my cabbie a few years back. With coupe seats the top of the seat back extends slightly above the parcel shelf so small items on the shelf don’t fall off under braking. I’ve seen seats made lower so that the hood studs are available to use but they look a bit odd to me as the seat is back is quite low. Not having the hood fixed down doesn’t make much difference IMO – stationary it sits perfectly, at speed (100kmh) the centre lifts a little but nothing dramatic. My 2 cents worth.