The easiest way to remove is to drive the center mandrel out of the rivet with a small punch, after mandrel is removed drill out the remainder with a #21 drill bit. If the skin while driving out the stem drill a big hole in the end of a 2X4 (big enough to clear the expanded legs) and use it for a backer.
I use my bucked rivet "drill guide" I purchased from VTS. It is just a drill guide that senses the OD of the rivet head and thus positions the drill bit center in the domed rivet head. It holds it in that position while you drill out the center of the rivet.
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