Just use the existing hole.
My malibu has redundant drain plugs. I used this fitting in lieu of drilling two holes.
I've got two rear sacks driven by parallel Johnson pumps:
- One sack has a new 1" hole and 1" shut off... the rest is 1" tubing, fittings, etc.
- One sack uses the existing 3/4" hole and a 3/4" shutoff. ... the rest is 1" tubing, fittings, etc.
The fill/drain time between the two sacks is negligible.