Two Speed Mainsheet Systems Gross-trim/fine-tune mainsheet systems are easy to install and use. For fast trimming pull both tails of the mainsheet. For fine-tuning, pull one tail and the purchase doubles. Two-speed mainsheet systems come in three configurations for boats from 22 ft to 39 ft (6.5 m to 11.8 m), with mains as large as 3502 (32.4 m2).