I've used many elms like that. The heartwood is superior in compression. I think it will be fine. I probably wouldn't split it. I also wouldn't be trying to get more than one stave out of it, if I got more than one great but all my effort would be concentrated on getting one beauty out of it(the reflexed side). If you fancy a trip up north anytime I could show you a place where there are hundreds of elms upto 8 inches that you could cut with no problems.