Dual extruder head alignment pattern

With my FlashForge Creator, I didn't have any success with the built-in extruder alignment pattern--the settings that resulted didn't improve my alignment.
So I evolved a test object that makes it fairly easy to measure the errors with calipers. I print in MakerWare to get the wipe wall, but set the offsets using ReplicatorG (because MakerWare can't talk to machine parameters for a FlashForge Creator running SailFish--some kind of map error).
I found it helpful to plot my errors vs settings on graph paper, eliminated a lot of dumb mistakes due to forgetting which sign convention I was using for the errors.