That might work if the guard is well-bolted in (sturdy) and you'd hammer athwartships, but I'd hesitate to do it in a fore-and-aft direction. Maybe get the mate to lean on the guard?mark the locations with a sharp center punch.
That's where the automatic punch comes in handy. No hammer. Just hold the tip in place with one hand, and push. It may take a few strokes to get a good mark on stainless, but it should be good enough to start a small drill bit.That might work if the guard is well-bolted in (sturdy) and you'd hammer athwartships, but I'd hesitate to do it in a fore-and-aft direction. Maybe get the mate to lean on the guard?