The 57 mm Carbo Fiddle Block is a great, light weight, high load, block that you can use to add purchase. On the Flying Scot we use it for the 3 to 1 mainsheet at the end of the boom. This is the standard rigging for the new daysailing Flying Scots. The 3 to 1 mainsheet is linked below.
Low-friction Carbo Air blocks are lightweight, strong, reliable—and affordable. These small, compact blocks have very high working loads for safe, easy trimming.