The correct way to wire your battery up is to install two
fuses, one, higher value fuse (say, 25 Amps) at the battery and a second, lower value fuse (say, 20 Amps) at the converter/fuse box. The extra fuse at the battery end protects your electrical
system should a short occur between the battery and fuse panel, and using a lower value fuse at the panel makes it so, in all but one case, the fuse at the fuse panel where you're more likely to go hunting for a blown fuse will be the one to blow if something electrical
You should also put a fuse at each end of the charge line on your trailer hookup, a high-value fuse at the tow vehicle battery end, and a lower value fuse at the trailer end.