More alternator questions

[GSanders17]

So I called DC power about my alt again and the guy said he had to talk with the techs to see what may be going on. He made mention that my 300 amp fuse i have in line with the 0 gauge running from the alt to the battery could create alot of resistance. Really? Do you not want some sort of protection for the wire? Even if it were actually the cause for the voltage to be low why would it have gradually gotten lower day after day? As I have said before the big three is done and with that 0 gauge in place even the factory alt would charge at 14.7 while the engine was cold. I have also checked the belt everyday since the voltage started dropping and it is still just as tight when i first put the alt back on.