I figured it out. The dxf files open in VCarve by default into inches, but the program DOES NOT convert from mm to inches automatically. So a job size that is set at 6180mm shows up as 6180in. All you have to do is open the file, click the mm option in the job set up pane, then hit ok. Then go back into the job set up pane and change to inches.
The dxf file is still much larger than a 96x48 sheet of plywood, but that's how the files are built. One converted, the actual vectors to cut fit nicely in a 96x48 job size once all the text etc is deleted.