Bill wrote:
I don't want to spend upwards of $45 for a 4" hole saw
and arbor for this one hole...



If you are going to do the work yourself, you need
to use the RIGHT tools!

I would also rent some scaffolding and NOT stand on
a ladder to do this work*. Medical bills can be
a LOT more expensive that what you would save
not using the correct tools.

*What happens when the hole saw gets stuck and
the electric drill starts to turn your body in
a circle? (While standing on a ladder.)

You would rent scaffolding to cut one hole? Having never rented
scaffolding, my guess is it would be cheaper/easier to just call a
contractor and have him/her cut the hole.