TB that 50mm is for a standard weight of rider only of 35kg, you will have to adjust according to weight, what is his body weight, also check the preload on the rear spring it should be around 12mm, get it set to this and put the shock rebound adjuster on 5 and you should be good to go, PM me for more detail if you need, if you start from standard settings you can then tailor to suit the riders weight and ability changes as needed, cant wait to have your little one at one of my MX schools Mate, bring him up and I will have him running circles around you(if he is not doing that already):woohoo: :woohoo: