Mainsheet length
On my 28.5, I am using 3/8" StaSet at a length of 68' through a 6:1 system with two triples for my mainsheet. To determine length, push your boom to the shrouds, measure the distance between the blocks, multiply that by the number of runs between the blocks (4, 6, etc.), and add a comfortable tail length.The diameter of the cordage is dependent on what feels comfortable in your hands, the capacity of your blocks, How much weight you want in your sheet, and the type of line.