choosing lace patterns for EZ's Pi Are Squared shawl

[meriellyn]

I want to make the shawl from Knitting Around and I'm thinking about using a lace pattern rather than plain garter stitch. What guidelines do I need to follow to make the pattern work? ie. What stitch count repeat should my lace pattern be? 

[spaghetti]

Here is a lace version of the Pi are Square shawl.  Crazy complicated...but maybe it'll give you some idea? 

I haven't seen the original EZ pattern so I can't help out with any changes.  Sorry!