Cutting New Halyard Exits

[CJV]

Hi again..
So the boat's been in the water all winter, and the mast is up and full of halyards & lines. I'm re-considering using a jigsaw, favoring instead a grinder with a thin diamond cutting wheel. Does anyone have advice to the contrary?

I suppose I could cut one of the round openings and pull the lines away from the opposite side using a coat hanger, and then use a jigsaw. But the grinder strikes me as easier to control while on a stepstool on a deck.