The only way to tighten it would be to replace it with a new one from Choate that is slightly longer or relocate the screw hole foreward slightly and shim the back side of the hole to move the forend tighter against the frame. One way to do that is with a nylon or alluminum spacer epoxied into a new position in the forend, I've done this on my Superlight with a synthetic forend. I also floated the forend at the same time using the spacer as a sort of pillar.
Tim