Quote Originally Posted by Melzk View Post
...any advice?
About the only thing you can do in the slicer is change whether the outermost perimeter is printed first or last. If it's printed last, there's a chance that it will be squished to the outside more than if it is the first perimeter laid down.

The XYZ steps per unit are set by the hardware design of the printer and shouldn't require alteration unless something like the number of teeth on the motor pulley changes. Before I changed the steps per unit to fudge the printer, I'd try another slicer for comparison. For example, if you used Slic3r to print this, try slicing with Cura and see if there's a difference.