My son, 10 years old, is currently riding a CRF70. He really enjoys it and it suits him fine right now. I am looking and researching what the next step should be for him. He does not race. He may enter a few races here and there but they will be desert races. We ride mostly open desert/trails. I am not interested in upgrading the CRF70 because I have two othe boys to follow riding that bike here soon. I am interested in what the next natural progression should be for him. I do not want to go the 2-stroke route. I would prefer to stay 4-stroke. That is just a personal opinion, nothing against 2-strokes. What in the 4-stroke class would be a good choice? I know that the KLX110 is a great bike but it is the same size for the most part. I don't want him to ride a bike that doesn't fit him very well. Mind you, I am not very tall, 5' 8" and he isn't that tall either. CRF100, CRF150? I would like something with a bit more performance overall. Thoughts?