Apologies if I'm poking something meant to be left unpoked, but I had thought it was unsustainable on the scale of the tens of minutes or hours that RoW was meant to be usable for?
I mean, maybe I should just say the whole thing I had in mind instead of asking questions about the prerequisites for it - I wouldn't want to come off like I was trying to set you up into "agreeing" to something you didn't want to regardless, since I know that's rather a severe faux pas.
My impression of this road is that it's a drop off a cliff on one side, and the other side it's just a cliff - as in, a cliff wall rising up from where the steam wagons are to the next level of the Skull Road or whatever. What I had in mind was that the steam wagons would, absolutely, try to avoid driving over the big hole in the road - I'd assume the hole that resulted in a drop off a cliff for the Urmskaladrak would naturally have to be on the "outside" of the road where the drop off the cliff is, so trying to avoid it is pretty much a no-loss scenario since it doesn't add any risk. But at the same time as they're doing that, Mathilde would be casting RoW over the specially prepared will-consistently-trigger-RoW-because-it's-uneven/inconsistent-enough surface that's been set up (which is something that could be safely tested by volunteers attached to safety ropes to confirm it consistently triggers before sending a steam wagon). Not as something intended to carry the full weight of the steam wagon while it just drives right over the hole, but as a kind of failsafe so if while they're trying to avoid the hole entirely one of them does start to go over the edge there's something there (namely, RoW) to bear the weight of that specific portion of the steam wagon only, and only for long enough for the steam wagon to course correct or just move past the danger zone.
Would that, specifically, be viable? Am I even picturing this space correctly? It feels like if I am picturing it correctly then it should be workable, because if RoW can't support part of the weight of a single steam wagon for the length of one obstacle/hazard without Mathilde passing out or collapsing then how the heck have we been using it on all of them at once for (I think) hours at a time? For RoW to be effective with the steam wagons at all then it has to be capable of supporting part of their weight at a time, because otherwise it would do nothing since that's its whole function.