I'd consider sticking with the 57mm Harken bottom block (I assume you are using the 57mm carbo ratchematic) and use a 40mm quad carbo top block.

I came up with a nice roving pattern for a 9:1 a couple of weeks ago - I'll post it this evening. That was based on the 75mm carbo ratchematic base with a 57mm quad top block and is for an F18, but should translate nicely to the smaller top and bottom blocks.

I have already put a 57mm base on the A-Cat to replace the Marstrom center sheeting (which I found high friction and impossible to cleat even for tacking). This is coupled with a 57mm triple carbo block with a small block hanging off the becket in an 8:1 arrangement that works OK. I intend to replace it with a 40mm quad and use the 9:1 roving pattern I mentioned already. I don't really need 9:1 but my wife will appreciate (the A is her boat).

10:1 on an A-Cat seems to be overkill - a good 8:1 or 9:1 with less friction will save the hands while reducing the amount of sheet used for adjustments

Chris.