I don't normally feel a big difference bewteen 3/8 and 7/16 line. Also I don't understand about tired and line size, the difference for me is my hands get sore.

I went to a ratchamatic block last year so I will comment on it. The big difference over older blocks is reduced friction. With the right size line, it feels lighter and more direct. When you screw up and twist the line or something it's just as bad as any other.

As a first step check your system. Your enemy is friction. Does the line go the right way through the rachet? Wash the mainsheet and the blocks in freshwater and dish washing liquid. Squirt some dish washing liquid on the bearings. Now look at the mainsheet and try to eleimenate as much friction as you can. When you sheet in hard is the mainsheet touching it's self and rubbing where it goes through the blocks? If it is try to reroute it.

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