I know, but it's not as large as Pistol Poker or BK2000. The "playable area" of the individual Black Hole and Haunted House playfields are just not that big; even though the playfield part itself extends way larger than most (for mounting purposes).
Now, if you COMBINE uppper+lower play areas, BH and HH would be 2nd and 3rd for largest TOTAL "play areas added up". However, Elektra would likely move up to 4th largest.
Technically, Medusa does not have an "upper" playfield. Nor does Grand Lizard.
I'm thinking Banzai Run certainly qualifies to be 1st on the list. I have added some others I didn't see mentioned yet. I'm sure I missed a few.
Here's how I see it so far LARGEST TO SMALLEST single extended "playfield area":
BK2000 (counting the wire-form overhang)
The Gumball Rally (Homebrew)
Pinball Champ '82
Time Machine (Zac)
Escape from the Lost World
The below are all relatively small beans but I still tried to rank them:
Doctor Who? (not sure about this qualifying as an upper playfield)
Transporter the Rescue? (not sure about this qualifying as a playfield at all)
CV (not sure about this qualifying as a playfield at all)