What printer are you printing on? Replicator Dual? Yeah the long flat prints really let you know when your bed is not level, or in my case not true. The middle of the HBP is higher than the corners so its a real bitch to get a good first layer on mine. I tend to not mind as much if the center is too thin on the first layer, as long as the nozzle doesn't drag. The corners are where the bond has to be the strongest.