Let me bring this back from the dead and ask this:
I have a dedicated MKII that has the same problem from running it via the MKII PCB.  When I hooked up the AVGA and ran MAME, it also had the same problem.  I can adjust the verticle settings, but then it gets so streched, parts are off the screen.  How can I keep it from curling at the bottom?  Thanks anyone who can help!