Don't waste money Robi ! Just grap or buy a small (series 30 I think) block, release one bolt that goes through the eyestrap (and cleat) from the becket. twist the eyestrap away a little, run the little block over the eyestrap and fix the bolt again. Now you can run the sheet through this small block and tie it off to the becket on the upper block. Presto ! A 7:1 system for the expense of no more than one small single block.

I upgraded my mainsheet like this in literally 10 minutes. (I spend about 6 minutes of this rerunning my sheet line to make it rub less against itself)

If you have a graving for Harken than go ahead an buy a new block. Otherwise save yourself a 100 to 150 bucks and upgrade your current system.

Wouter