95mm level bed test print

I needed to calibrate, verify, "tram" my print bed since prints in the back corner where failing. There are numerous calibration test prints, but most seem to be too large for my Printrbot Simple.
This file creates a 95mm x 95mm square that is 0.25mm high with a 5mm border.
I print this with a layer height of 0.3mm and 3 loops on the perimeters and diagonal infill. The 2 photos are the same 5 print jobs in order from left to right as I adjusted both the height of the four corners as well as