Dyne's 99-99 Build

[Dyne]

That concept art makes it look like the original plan was that Four-nines would move by rolling, using the centre ball as an impeller and the yellow-and-white arms as outriggers.  Which makes me suspect that having him float was an animation shortcut.

I think flying in general was always intentional as the drawing does also show the whirlygig motion that he uses (center right), along with the micro thrusters.  However, I think you might be right ... maybe he wasn't originally meant to fly apart from those motions, but the animation omitted the rolling mode in favor of hovering.

Strangely, it never really occurred to me that he might have been intended to roll (in spite of being well aware of the wheels in the arms), probably because I didn't see this art until nearly a full year after I saw the episode.  

Now, if I were to attempt a rolling version I'd probably scale him up a bit, just to have some more room!

You'd need it for adding a drive system, especially if the lower dome became a full sphere and you still cared about the head's omnidirectional movement or any arm animation. I'm not saying it's not doable, especially if you didn't care about the head or arms, but I fear it'd be sort of like designing the Sphero R2-D2. Smaller builds have a tendency to be more of a pain as they require tighter tolerances and denser packing because, while the droids are smaller, the off-the-shelf components we have access to usually aren't much.

The idea reminds me of M-O from Wall-E, though, who is on my list of builds to do eventually.  I know rolling versions exist amongst the Wall-E builders like Matt Hobbs, and there are files in that club.

But that's not on-screen so not canon in any case.  And this build is very cool!  Eebel's build does a good job capturing the animation look, but it seems a bit bland in real life.  Yours looks more like a "real" droid, to my eye.

Thank you.

In fairness to R-Duo, this was also his first public appearance. I believe that he was still being worked on shortly before the con, and there undoubtedly wasn't much time for weathering. I suspect he'll get some love soon to help him look more grounded in reality.