"Yeah." Sans nods in reply to their first point, this time without hesitation. He's changed back before, after all. If he was able to replicate the first effect with backwater substitutions, Neil should be able to replicate the second effect with the same. And hopefully so no one else has to lose an eye.

...their second point is a little harder to agree to, for a lot of reasons. Sans ducks his head, but finally mumbles: "I'll try." He'll try to remember to ask, try to find ways to ask if he thinks of anything. In the meantime, however, Frisk should at least know who the ones in the know are. "Ask Serif." His other self probably communicates better with Frisk than he does almost anyone, and so might be best equipped to fill Frisk in on their efforts - especially with Neil still laid up.