Don't do this. You can't use the already in use fuse as it is dedicated for another run.
Just re-run brand new wire for the power, it is not that hard and add your own fuse.
It's a simple fix.
I ran a 12GA bonded pair wire from the battery, inline 15A fuse as close to the battery + terminal as possible, through a grommet on the passenger side, up under the dash, zip tied as needed.
Then at the acc outlet, disconnect the OE connector, crimp on a 1/4" spade connector to each wire, and push them on to the terminals on the outlet. You may need to smash the connector down a little bit to get a good tight fit onto the terminals.
Done. I think it was a 5 minute job all said and done, and most of that was finding a good grommet location. I can post pics if you need, but it's really easy.
The center of the acc outlet is positive, the outside is negative. You'll see which terminal goes where on the back of the outlet.
I left the original wire and connector in tact and behind the panel. It's not going anywhere, and everything in the area is plastic, so there is nothing for it to touch and short out on. You could probably pull the fuse for it, but I'm not sure if it controls other circuits and not worried enough to find out.
