Oh, this is awesome. I was going to try to figure this out myself if nobody else did. I wish every emulator supported 240p.
I think it needs a little bit of filtering though, it looks like a big chroma mess via composite. Looks fantastic over component, though!
BTW, after a bit of digging, I figured out from another post that if you set "joysticktype=fcs" in the .CONF file, you can load up DOSBox, hit CTRL+F1, and it'll let you bind arrow keys to the d-pad on the Pro Controller (otherwise binding them seems to have no effect in any game).
I didn't check to see if this messes up games that support analogue joystick, though.