Blue Sea USB Fuse Questions

I ordered both a 4.5 A and a 2.1 A Blue Sea USB chargers and need help with what size fuse to use in my fuse block. the 2.1 A will have about a 12 ft run on 12 AWG wire and the 4.5 will have ~6 ft on 12 AWG wire.

 

In a perfect world the power out is the same as the power in, so 4.5A @ 5 V is 22.5W and 2.1A @ 5V is 10.5W, which is 1.875A and 0.875A, respectively, @ 12V. If you're running both off the same circuit, that's 2.75A total, so I'd use a 3 amp fuse. If you're running separate circuits, 2A and 1A fuses will be fine.