Hey ccrunner, this looks very much like something I've been trying to work on. I just got a new Evolution and have been less than impressed with the range of the internal wifi and wanted to add bluetooth as well. Rather than the Silver version of the board you bought, I went with the Gold to get that range boost.
My initial plan was to wire directly into an AUX port in order to draw power for the BT module using the available +12 and a +5 regulator, negating the need for batteries or external power hookups required with the usual bluetooth options. With everything wired up and powered, I've had no luck communicating with the scope but I can see the port and watch data come across the link when slewing manually with the HC. I've only just started playing with this scope and am still learning quite a bit about interfacing, so I could very well be missing something with my plan.
Looking over the datasheet for the MAX232, I know where I need to route the wires to match your setup but I'm wondering if you've tried updating the firmware on the HC or MC over BT since this mod.