We are already rolling for severe miscasts. Mathilde is described as being exhausted and even travelling through the ship is difficult when relying on her windsight. And that was before she was struggling with muscle ache and milky eyes caused by her minor miscasts.There's 50 left tops. And likely we're going have a lot less than that. It's worth the attempt now that we've found a method to do it that reduces almost all the risks. Mathilde using the powerstone can tell all the dawi on board to extinguish the lights and how many times to bang on the door in a short time frame to confirm the lights are extinguished.
Then the only risk is miscast rather than the dangers of getting screwed by SoS failing it's not risk free, but it's removed the most substantial risks.
The update explicitly calls out that going back will mean rolling even more dice than this time. Never mind that we also have to count on potentially up to 50 Dawi, who are alone, scared and possibly drowning to obey a voice they hear coming from nowhere telling them to turn off any light source they have. That sounds like another roll to have them not discount us as hallucinations.
Mathilde has to cast a massively boosted fiendishly complex illusion (so increased risk of major miscast), followed by another up to 50 uses of substance of shadow. Not to mention however many times she has to cast marsh lights to check if everyone is still alive. And ensure she can find enough aii pockets to keep herself alive.
Do you roll those dice again and in larger numbers for fewer Dwarves? If every sealed room was filled to standing room only, that could represent as many as fifty or more, but if there's at most one or two in each, less than a dozen.
This is incredibly risky.