I have an old 100amp 8 ckt fused panel I want to add a sub-panel . Would it be correct to come of the two lugs at the bottom of the bus bar with #6 and feed 50amp main breaker in the sub panel which is only 4ft away or can I just come off those lugs with #3s and go into the main lugs of the sub panel, Being that the main are 100amp fuses.