Am I okay to piggy back only the step and direction pins from the test headers to use to signal my external drivers? I am curious to see how the external drivers at about 3 amps may affect my results.
Yes, that's OK, the STEP and DIR pins are driven the same whether the drivers are internal or external. You may need to use the M569 command to increase the step pulse width for your external drivers.
Thank you for the help David! I'm running a test with the external drivers now.
I have the Duet underneath my Kossel with the wifi antenna protruding slightly. If the wifi signal is reasonably strong in the room where the printer will be, then it should be OK to put the Duet underneath the bed, assuming it is not surrounded by a solid metal frame. There is no easy way of extending the antenna, and FCC/CE regulations make it impractical for us to offer a version with an external antenna.
The stall detection isn't reliable at low speeds and the stalled status is only updated once every full step. So the stalled status should be ignored unless the motor is moving at a reasonable speed, or trying to. Also, the stall detection really needs to be tuned to the type of motor you are using. I'll probably add some sort of auto tuning for it in a future release.
What about a silicone type heater rather than a PCB heater? They tend to be a bit better in my experience. Also, add some sort of insulation if you haven't already. Even a very thin reflective barrier can make a big difference.