I would suggest the tall hoops, if your not sure sit in one and see where the top of the hoop is relative to the back of your head and imagine what might happen if you get a shunt from the rear. For me it was level with the centre of the back of my head and I wouldn't want to have that hit me at speed, tall hoops on mine! Apart from the fact that the normal ones won't protect much in the event of a crash or a roll
