Formatting a high-density 1.44M floppy as a single- or double-density 400k/800k floppy works well enough, but you won't be able to reformat it back to 1.44M if you ever need to. You don't even need to tape over the hole for a Mac 512k - that is only necessary if you need to fool a Superdrive into believing it's a 400k/800k floppy.