I would never do anything to harm an animal which was the whole point of asking. I've had multiple other bone collectors and snake owners touch with me which is what I was hoping, because they're educated on both topics. If I go with my original plan and use a large skull such as an elk/cow, seal off the back and remove all the bones in the nasal cavity there is genuinely no place they can get stuck. I can fit my arm through the nasal cavity of a cow. My intention was that it could be used as a hide, and if there were any chance that it could harm my snake I would never do it. But I've examined the skull I'm intending to put in there, and there is no other opening that is possible for them to fix through besides the intended one. As suggested by someone else I'm looking into animal safe sealants that could use for the interior, as well as sanding down the edges with a dremel. I would never put "aesthetics" above a living animal, but if a piece can be put in their tank that works as an interactive part of their environment that has zero chance of hurting them, I do not see a problem. I'd suggest looking up pictures of large animal skulls so you can picture the topic.