Jive is one of the only dances that allows you to have a bit of a jumpy skip in the chasse movement. This is NOT, however, license to hop all over the place. Throughout the Jive, especially with the two chasses when moving side to side, you should imagine your head being kept at one central location and that your feet/hips are swinging in a pendulum style movement underneath you.
Keep all your movements small, as the Jive gets very fast, and make sure that you are not transferring your body and head weight back when you do the rock step. You need to make sure the heel of the back foot touches the floor, while maintaining a body position that has minimal change. (If you allow your body weight to transfer back with your foot, you will firstly be unable to maintain the speed necessary and secondly will possibly separate yourself too far from your partner.)
The Jive should be light and fun and the hold should remain flexible and much more relaxed than any ballroom stance.