Had some time today, and so I finished putting together the bed support and worked on tramming the bed and aligning all of the axis. I still need to work on the Z, however I was able to get the X and Y square to the bed within about .03" which isn't too bad. To do the alignment, I clamped a small bit of steel to my toolhead, and then attached a magnetic base dial indicator. As I moved the X and Y position, the dial indicator swept the bed, and I was able to watch for height fluctuations. Picture forthcoming.
I'm going to write some test G code to help ensure that the X and Y are perpendicular later this week. it should be fairly easy to draw a couple of lines and measure with a square. For Z, I'm going to use a square relative to the tool frame. Since I know the bed is good, that should be a fairly simple solution.
I'm working on a better loading solution for the G code. Since all TinyG needs is to have a streaming program that knows software flow control (Xon/Xoff), there's really no need to have a full-blown PC attached to the unit when milling. Since I'd rather not burn the workspace space (and power) if I don't have to, I've been thinking about other options. I've decided to take a Chumby One that I had lying around and use it as the serial link to the TinyG. At the moment, I have minicom running on the Chumby, and I'm feeding it instructions manually. My hope is to write a simple menu and status program to take advantage of the Chumby color LCD touchscreen, rotary encoder and button.