Take the plate out. Turn it upside down, lay it on a smooth surface like a thick sheet of steel or vise. Peen it with a hammer to enlarge it where it is sloppy. Then refit it to the stock. Simple. Most so called gun makers suffer from the notion that wood is the only thing you can change or alter. All master gun makers work with the metal as much as the wood. No offence intended. Don't peen on the exterior surface. It won't be any uglier than it is now.