I am surprised no one has replied yet. Hmmm. I know that Harken has a 4:1 carbo ratchet system for the Wave, which I am considering. You can find it under "articles" on their site
http://www.harken.com/blocks/blocks.php
Maybe go to the Harken site, and see what they have. I remember seeing the GTWY uses a 3/8"main sheet, (is it 5:1 or 6:1 on the GTWY?), I think that is a 40mm block if you go w/ the Carbo blocks, which are really nice. Harken also has a block size calculator, to help you choose. I think if you just went to the site, selected components similar to the stock config, you would be alot happier w/ the smoothness and adjustability of the Harken stuff. Not cheap though. Expect ~$200+ for a system.