I understand the "whippy" comment relative to a Rem 870 20G at skeet as I have one and have had similar experiences. I did correct the "problem" with a screw on magazine weight that significantly improves the gun movement in a controlled target game like skeet. With this change, I can usually shoot this gun about the same as one of my target guns which weigh considerably more. Regardless of the gun that I shoot at skeet, I always shoot low gun and do typically use a rapid swing through with very short gun movement - sort of the "ambush lead" discussed earlier.
Z