Many MOCs (My Own Creations) are fairly fragile. I was terrified of figuring out how to move L3-G0 and that was in fact one of my first experiments. I had tons of bungees and other stuff ready to move, plans for a plywood base and all sorts of stuff. Moving the Lego Space Needle is pretty challenging. I feel happy that it only takes 1/2 hour (usually) to get it back together now. That's only 4500 bricks. L3-G0 is closer to 16,000 bricks! So I figured it'd be harder.
He's only 60-65 pounds or so (almost 30kg), so unlike many other R2-D2 builds he's not too hard to lift.
The first part is to take off his head (remembering to unplug the wire helps) and stick it on the car seat, careful of the holoprojectors. I put the seat back up as far as possible, but don't really worry about strapping it in or anything.
Then we pick up L3-G0's body and put it in back. The front foot shell comes off and the casters get shoved in around the rear seat's mounting point. Hooking the bungee around the top of the foot is about the only hard part since the hooks don't have much room on the mounting point.
And then last is to merely hook the back seat belts around the central foot guide post, pulling them to ratchet tight (like you would a child seat). Again, watch the wire on the top.
The sad thing is that getting the bungee is sometimes tricky, and the last step, the seatbelts, is so simple, that I've forgotten about the seatbelts about three times already. Fortunately the last two times I caught myself, but on the way to Hosik's science fair we were late & rushing, so I drove down the driveway with them off. I was reminded to fix it when L3-G0 fell over on his face. Fortunately it didn't do much damage.
Anyway, once he's secured, the model's ridiculously stable. It barely moves and I don't need to be nearly as careful driving as with the other models. (The Space Needle wants the sections I divide it into to fall apart, and the Lego Disney Wonder's nice wooden platform has slippery velvet on it, so it wants to slide around. The worst part for L3-G0 is putting the front shell back together.