Don't copybits from the gworld to the printer - copybits from the gworld to the gworld.
myPic& is now a copy of the contents of the GWorld. (Copying a picture on top of itself leaves no visible effects, but if you have a picture open, the copy operation gets saved in the picture.) You can draw this to the printer and it will execute as one bitmap operation instead of many line-draw operations.
myPic& = FN OPENPICTURE(gworldFrame)
CALL COPYBITS(gworld, gworld, gworldFrame, gworldFrame, you know the drill)