North 2025 Sonar Mast ShimSONAR MAST SHIM 1. 0 Trim Adjustment Shimming your mast under the leading edge will trim the board nose up and help enable you to regain a more comfortable stance and control over the board at higher speeds. Shimming the mast under the trailing edge will trim the board nose down at lower speeds (e. g., pump, dockstart, or downwind), helping the foil to engage foil sooner. NOTE: North boards and foils are designed to work together for their intended