I personally don't think side-clips do squat for action strength. It's not obvious how they might prevent side-to-side play in a gun which is otherwise on face and tight. By deffinition, a loose gun would bring the outter edge of the barrels away from the previously nicely fitted side-clip thereby negating any value of it as an anti-pivot feature.

I did a Google search, and found one version of a 'side-clip' with obvious merit and value. Enjoy.

http://cgi.ebay.com/Slim-Cut-Thong-w-Side-Clips_W0QQitemZ260140685390QQcmdZViewItem

"The price of good shotgunnery is constant practice" - Fred Kimble