well, I'll chime in here to report that, some months ago, I decided to try my Walkabout on its side in a rehearsal.
Comments above about the function of the passive radiator not withstanding, it did change the sound of the cab.
To my ear it made the deep full low end that the Walkabout is known fo drop out to a noticeable degree, made it a thinner sounding cab.
Because of all the smart/technical types here on TB, I was prompted to read up on passive radiators and how they function. I do understand that the bottom loaded radiator does not produce sound itself, and really just operates in lieu of a port for the purposes of tuning the cab, thus allowing it to deliver more lows than the simple box size would suggest. But, setting a Walkabout on its side changes the tonal character of the amp. The same is true of the passive radiator design Scout cabs too (I have a Scout 15 that I tried it on).
No idea what the explanation is, but there you go.
+1 ! I tried my Walkabout Scout on it's side, and also elevated on a stand and my perception was that of less fullness when it was off the floor, or on its side. It was easily noticeable. Especially at louder volumes. I ALWAYS prefer my Walkabout Scout vertical, on the floor.

