Yeah... I know... already a thread on this... but that thread seemed to go nowhere. There is definitely problem with S3D and possibly GPX with dual extruder Rep1-like machines. I just connected via USB to my FF (something I only do to upgrade) and brought up the machine control panel. Connected fine and jogged fine. When I set the extruder to T0 the right extruder heated up correctly, when I set the control to T1 the left heated up fine. So... it's not a backwards connection to the controller board.
Then I sliced a cal cube and printed using the Replicator 1 (Left Extruder) presets in the added process. It went to the right extruder (T0) even though the process showed everything pointing to T1.
Thanks for an AWESOME printing app!