Here you can find general information about jockeys:

http://animal.discovery.com/tv/jockeys/horse-racing/jockeys-101/general-facts.html

There is no minimum weight for a jockey, he would make up the needed required pounds by adding lead weights. Maximum weight would be the designated weight that the horse is scedueled to carry , most often a jockey would not get many mounts if he weighed more than 118 lbs.Same with height he could be 3 feet tall or 7 feet tall as long as he could make the designated weight that the horse was required to carry.

Why do jockeys ride standing up in the stirrups

Why do jockeys stand up in the stirrups?

They stand up in the stirrups to create minimal movement on the horses back and bc the horse's stride is so fast it would be very uncomfortable to sit on the back . mostly its just easier for horse and rider. keeping in movement and be as light on the back as to the riders max