i agree with rhona and pammy. i think i'd worry too about him hurting himself, either in the short or long term. could you get some planks of wood or something, to provide a temporary ramp for him? then you could let him go in and out without needing to stop him and pick him up.
barkers scared my mum when he first went to visit by happily jumping off a garden wall (about a metre drop) onto the lawn.
he would have done it again without a hesitation but we blocked it off. i think you do have to protect them from themselves whilst they are very young. they seem like such resiliant little things
but we're constantly being warned of the potential long-term problems.