Okay,

Might want to switch which motor is which and see if you have a dead board from the maker (has happened before) or if you have a multi-meter checking you are getting good voltage. On the Heat issue, from the voice of experience as Jazz, JohnS, Andy, and a host of others (including Jonathan who does not always explain why) who helped me pointed out that all in one boards have issues (I have let the smoke out more than once). I currently run a PMDX-126 board and the voltage is right at 67.5V most times (Supply to the shop changes by about 1 - 1.75V and that affects the Voltage at the machine).

Heat from my experience is more of an issue at low voltage than when running at or near max voltage. It takes over four hours run time these days to get my machines motors to more than just slightly warm. I will let Jazz and Jonathan and others explain the importance of Voltage and Current and why running to low leads to heat issues.

Good luck on the build and the advice you are getting here many folks pay money for. -Michael