not having a fox I have heard about the upgrade, but this is the first that I have heard about the 200 amp fuse........ Is that really what they recomend?
A 3 foot section of 4 awg cable is only rated at 150 amps max fellas. You could take that length of 4 awg with its fuse and short out a good battery and the wire will melt before the fuse.
http://www.knukonceptz.com/assets/pdf/PowerWireSpec.pdf
you lookin at 0 awg if you want something that will last more then 200 amps.