Dana, I was a bit uncertain at your thread title at first.
Elk have antlers.
Sheep and goats have horns.
Keep in mind that antler is an organic material- basically bone - that will shrink and expand with the surrounding humidity. Care and attention is needed from the beginning when working with it.
To avoid many problems, a person can leave the material a bit larger than the surrounding areas so that when in a shrinking "mood", it will still be a little taller and not have an exposed edge.
Stabilizing will help - a lot. Making sure its professionally done.
Another thing to do is to be sure to remove all of the center core, or pith, months in advance. This material seems to hold moisture rather well and keep the entire antler piece wet. Remove it well in advance of using it to ensure the antler is totally dried out.