Brian, sorry I didn't see your response earlier. I wouldn't want to make tusks out of two separate pieces. If you were just doing small fangs, sure, no problem, but I found it hard to stabilize them when they weren't attached in the middle.
What I did was molded the tusks, then made a separate blob that attached them and then mashed it on my teeh and whittled down the outside through a combination of heating it up and removing excess and cutting excess off with a utility knife after it cooled.