I have an 8:1 on the Blade (3 bottom top block and two small ones in the middle (I added the 2 blocks afterwards)).
Since I don't cleat during regatta's I still found a 'standard' 8:1 quite heavy and had the feeling I could sheet in for max power.
Now I have a tapered main sheet and this is just great.

The only problem with 2 smaller blocks in the middle can be that they touch before you can fully sheet in. I have about 7cm between the 2 left.

Gill