When you see that the mounting bar from your wing rigger has worn a groove in the mounting blocks you know that the adjustment of the set screw is past due:
The conical point of the set screw fits in a matching hole in the end of the mounting bar and should be adjusted so the mounting bar never touches the block. If the set screw is not in far enough it no longer locks the mounting bar in position and the rigger can move from side to side and up and down making balance and power transfer less accurate. PS – you might want to get your hearing checked; because, there is often a creaking noise every stroke.
Proper adjustment keeps the mounting bar 1/2 mm (.02″) above the block and the screw should be adjusted so that the mounting bar is about 1/2 to 1 mm away from the vertical face of the mounting block.