Attaining new heights aside, Oscar remains the Spider-clutz.
This evening, we fed dinner Oscar in my office (working closer to the stairs, with the ultimate goal of feeding him downstairs). Billy showed up, causing Oscar to abandon his dinner for the monorail (aka the straight wide flat railing for the stairs), and Katherine started to take Oscar's remaining food in its bowl into the library.
Oscar followed along on the railing, watching Katherine as he went. Or tried. He made it three feet, didn't watch where he was putting his feet, and fell to the deep stairwell side of the railing. After much clawing and a gouge in the stairwell wall, he made it back onto the top of the railing, to our relief.
Of course, the one true Spider-cat has recovered from worse mistakes, but somehow I suspect Whitey would not have made this mistake in the first place.