From the Harken site. A little small, but it looks correct. You can see the top block is oriented 90 degrees to the bottom block.

Things to look for when experimenting with roving patterns: Does the top block get pulled over at a funny angle under load (this will cause the line to jump off the blocks and incur a lot of friction)?
Do lines touch one another?
If lines are close are they moving in the same direction when sheeting in or out?

Chris.