there is 7mm clearance from the bottom of the arm to the hull side, so the "L" shaped bracket is 2.5mm thick, and the guide arm is made from 3 pieces 1.5mm thick, the hull blade bracket is 2mm, and the brass guide blade is 1.3mm thick, so it runs inside the groove, you can use this modification on the standard swing arm, you just need to file a flat on the rounded bottom of the swing arm so the "L" shaped bracket fits snug, have included the templates I used so you get the idea, and pictures of the first steel guide and the alloy one fitted






regards
Jeff