Originally Posted by TheHubbardBus
cut the hole now, which would seem to be easier before being mounted,
before what is mounted? the AC or roof-hole-patch?
I would cover the hole with sheet metal now with 3M Urethane seam sealer and 4-8 screws, then remove the patch, cut open the hole to the size the new AC unit, then install the AC.
I never like cutting into my vehicles, and would put it off until the project is 100% go forward. Mice may chew up your already purchased AC unit while it is in storage waiting. A new better unit that is smaller, cheaper, more efficient, and cools with more BTU capacity than the one in the store you have your eye on may become available.
Who knows what tomorrow may bring? (no I didn't make that up, but it's a good saying)