The RK05 controller is a Data Break device and I have no idea if your approach with the PIC allows the pic to directly talk to the 6100's memory.
Doug,
The design as it stands does not support a Data Break interface.
I suppose I could add this but could I also emulate the RK05 with a custom handler?
I've started looking at the SerialDisk project and it looks like something similar is done there.
Not sure how difficult it would be though.
-Bill