Great going, teachop!
BTW: I'm not sure if this is helpful to you, Paul, or anyone in this thread, but have you checked out the GEVCU.org project?
http://gevcu.org/
The purpose of the project is to create a control unit for DIY electric car conversions, namely so they could talk over CAN with the DMOC controller which drives the Siemens AC motors. You can actually buy one at EVTV.me, but everything is there on the site to both build your own, including the software to run it as everything is open source.
They have succesfully got CAN working (supporting two different CAN transcivers, to boot) on the Cortex-M3, and the libraries they have developed are apparently fully loaded (masks, filters, extended frames, multi-speed, etc.). If you check the hardware tab, their initial prototypes used an Actual DUE connected to the main board, but the latest version is a custom all-in-one board incorproating the ATSAM3X8EA-AU. I must admit I'm quickly out of my depths both CAN and hardware related so not sure how that compares to the M4 used in the Teensy 3.1.
Also, if you check their schematic of this board, I really like their choice of transceiver, TI's ISO1050DW, as it provides full isolation from any nasty spikes or faults that may happen on the CAN bus, protecting Teensy and anything else hanging off of it.
http://www.ti.com/lit/ds/symlink/iso1050.pdf
One more: check out their nicely filtered and isolated 3.3V power supply on the schematic, too, as well as the fully isolated I/O. This thing was built in-car-tough.
Anyway, great work so far, and I hope that helps!