Well, in the end it is bad news i guess.
the 256MB RPi doesn't actually have enough menory t pint anything other than simple shapes with pronterface.
I started using pronterface running on a VNC session hosted by the RPi. It ran out of memory very quickly, and printing anything other than very simple shapes was a no-go.
I then shut down the vnc server, and set DISPLAY to point at another linux machine. With this I was able to run pronterface on the RPi, and print out a MB gcode file. There was ~50MB of memory free (nothing running on th eRPi except pronterface and a few ssh shells)
Next I tried to print out a 35MB gcode file. This ran out of memory, so I switched to using pronsole. With this I had no issue whatsoever loading my 35MB gcode file and printing it.
I am quite confident that the memory usage comes from trying to render the gcode file. If I could get a web-interface that did not try to fully render the gcode, I think I'd be set. For now, I'll use pronsole. It really isn't buying me much over loading the files into the sdcard, but at least I can pause, resume, change filament, and move the axes, which is all I really need.
I was also able to print using usb-redirector as I mentioned before. With a Windows computer running Repetier-host, it work great, but I only have a trial of the software, and it costs ~$70, and I want to do this with free software.
Using usb-redirector to a linux computer, I couldn't get Repetier-Host to work, but pronterface runs fine with any object size, and this configuration can be done for free.
I spent a lot of time trying to get usbip (which is like usb-redirector, but is free software) to work. I got it compiled on my RPi after much effort, but the client software locks up my linux machines, so this isn't really an option at the moment.