Heh, I just realized I can use a stupidly convoluted setup to get windows to use 1024x758.
Over an RDP session, the resolution gets set to whatever you resize the window to. So, simply run an rdp session over vnc!
On a linux machine, install tightvnc and rdesktop.
Comment out the line at the end that says: /etc/X11/xsession, and add a line that says:
while :; do rdesktop -f 10.0.0.10; done
(This launches an RDP connection, fullscreen, reconnecting if it gets closed or disconnected.)
Now, launch a tightvnc server with the appropriate size:
vncserver -geometry 1024x758
Now set the kindle to VNC into the linux machine and you'll end up with a fullscreen windows desktop. This is not ideal in any way, but it does in fact work.
In fact, for me it actually works with no more lag than straight VNC, though I'm using two virtual machines on the same physical box. So, they're probably connected by some crazy 100gbit internal psychic network or something; So that probably makes a difference.