I kinda of drifted away from the game (to some other[s]) when an answer didn't appear "soon" (tm) and overlooked your reply until now.
Thanks for pointing it out to me! Stacking is up for a go as soon as I wrap up one of the other games I am playing atm and I look forward to playing with this set.
1. Go to \Users\<username>\AppData\Roaming\Doublefine\Stacking.
(You can also open a Run... box and enter %appdata%).
2. Open the stackopt.sav.sav file with a text editor such as Notepad or Notepad++.
3. Look for the InvertCameraY setting.
4. You can switch between 0 and 1 to find the setting you like best.
5. Save and launch the game.