Thank you for your suggestion, Tessa. I was hoping to capture the vector of the collision but I now see that returning a reliable vector might be complicated by object types and scale. Your suggestion gets me close to the illusion I wish to create, I think...
Thank you, Fenix, for your insights into llCastRay and for pointing me back to your work in 2014. There are a number of good notions in that discussion that extend my vision of the effects from impact...