The way to get seized skidplate bolts out is by heating them nearly red hot, then they'll spin out fairly easily. I'm not talking heat-gun hot, I'm talking torch hot. I had 4-5 seized tcase Rubicon Express allen-head bolts that I welded big nuts to so I could use a big socket to remove them. While still smoking hot, I braced myself to pull hard with the wrench to break the first bolt free. No need, all of them came off with essentially no force required. I was shocked, I could have removed them with a 1/4" drive ratchet. It was just the heat from the welding that broke them free, a torch can do the same thing.