Its better for the snake too be cold then burn up and die. The way you are describing the snakes were shipped seems fine to me. Like Colin said the heat packs get up to 140 degrees, if that was directly under the snake it would burn the snake. We ship our animals in the same box that most people use(red and white boxes) that have 3/4 in. foam. We tape the heat pack to the top of the foam, And fill the box with shredded paper. Never had a problem doing it that way. Hope this helps.