Compact is short radius, wide base. Short radius is launching with the lead elbow bent.
You can teach it quickly. Put a bat down and have the kid put his feet at either end. Pick up the bat and put it back by rotating the shoulders inward until the lead elbow is behind the belly button. Take a 2-3 inch stride and keep the elbow there until the hip rotation moves it.
We do this with a Hands Back Hitter putting the bat 2-3 inches from the string. It takes one minute to teach with the above drill. We used it at Auburn University Youth Camp successfully on 107 kids. Please don't roll the wrist in the hitting area.....make sure the hips lead through contact......don't mention hands and wrist until they learn hip/shoulder separation
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