try something like
copy AUX:115200/8N1 CON:0/0/300/300
You can change the baud rate and control specifications as you like.
Same with the CON: window dimensions.
There are more things that can be added to the CON: spec, but I can't find the details right now. I know that Title and "AUTO" are also options, but I'm not sure of the order (or even if the order matters)
Have Fun!