I know there are a ton of sites that recommend adding your amp fuses and going up to 20A higher. But I wouldnt recommend it. Go with a fuse that is rated for your wire. 8awg = 50A, 4awg = 125A, 0/1awg = 325. If you're running a 4awg wire with a 125A fuse and your're blowing it because of the power you're running, you need a bigger wire.