You know, I don't recall anyone ever doing this for PC gear, even though the single-sided drive was definitely an option for the 5150 and clones like the MBC-550.
I guess it was because 160K just wasn't enough to start with.
I used to convert 10-sector hard sectored diskettes to become "flippys" for use on Northstar disk drives. I remember having to also punch a sector detection window in addition to the write enable notch on the side of the disk. I quit doing it when floppy disks became less expensive.
Was this not required for C64 and other diskettes?
If you don't like the round notches obtained with a hole punch, consider using an inexpensive metal nibbler, such as the Klein 76011. Takes a nice square "bite" of the right size: