Looking at this again, I still think I'm missing the obvious. I'm printing just fine, but the prints usually start around 40mm to the right of center so somewhere I have an offset error. I stripped it down to the simplest gcode for two tests: 1) This gcode puts the left extruder near the center point: G90 M83 G28 M218 T1 X37.6 Y0.4 T0 G1 X150 Y100 Z5 2) This puts the right extruder near the center point: G90 M83 G28 M218 T1 X37.6 Y0.4 T1 G1 X150 Y100 Z5 Is that what should be happening?
So if that works, I wonder why are my actual prints not centered near X150. In Simplify3D it's centered on the model, and in "GCode Viewer" it's also centered on the print grid. However, printing on T0, a 80mm wide x 50mm print is being aligned to the right of 150,100. That is, the center of the print is around X190, not X150 with a few mm of the print actually touching the X150 line.
