My day job has owned most of my headspace this month, so I've just gotten to the point where I have my three boards assembled and powered up. The good news is that none of them show any sign of shorts or any similar problems. The bad news is that not a single one responds to the programmer... and probing around makes it look like none of the reset lines got connected when I soldered down the processors. I don't think my hands are steady enough at this hour to fix it, so I will give it a swing tomorrow.
I did manage to get the CAN interface library ported to C and compiling, so I'm not quite out of the running yet. I'm not entirely confident of my ability to get beyond current control in the time I have left, but we will see.