Anthony, the QQ block in the Murrays catalog is a freewheeling fiddle block. Freewheelers won't work! You need a Harken (or similar) hexarachet or ratchamatic intended for a main. The ratchating feature is what provides the resistance so you can hang on under load.

Does your current block ratchat in one direction? It should. What is your upper block? One of the original Seaways or a Harken?

This season I upgraded my son's H14 turbo with a slightly used 6:1 Harken setup off of my H17. Worked great and a lot less effort to sheet in during high winds while on the wire.

If you're on a budget you could check out the new Hobie 6:1 main block intended for the Getaway. In the $70 bucks range and looked like a pretty good 6:1 unit.

Sail fast, Tom G