It isn’t mentioned in the manual but the car actually comes with a choice of bumper types. The one seen in the manual is the large bumper seen below.
Also in the kit are small corner bumpers as seen below. These save a considerable amount of weight but don’t give as much protection.
One other thing that isn’t mentioned at all in the manual is that the body posts can be mounted differently in order to move move the body shell backwards or forwards. There are three possible positions to mount the rear body posts. In order to match this at the front, the front posts are mounted as in the picture above to match the forward position of the rear posts and the opposite way round to match the rearmost position. In order to match the centre position rear posts should also be used at the front. In reality I don’t know of anyone who uses this feature but it is worth mentioning just in case anyone feels like experimenting.