howdy, first time poster, sometimes lurker.

I’m looking to install a two way or two in a 2015 Honda Fit and am designing the wiring for it. I noticed there is a “fuse box b” attached to the battery... there’s the main 100 amp fuse and three other fused posts. Two 70’s and an 80. They’re listed as RB x2 and a CAP. The third one - a 70 amp fuse is unused in this car and all I can find is that it is used for “cap main” but there is no further info about what this is. Anyone know any good reason I couldn’t use this unused post to pull power to the radio? It tests out as a good constant 12.44 (give or take) vdc. Is there anything special about this fuse box? Is it just pulling power direct from the pos batt post through some fuses?

thanks if anyone knows about this module.