I've sawn a bit of elm and used a few elm timbers, our barn is at least 50% elm. In my research on English framing elm and ash were second choices to oak.
In my area(ontario, canada), there is lots of elm that falls prey to what we call dutch elm disease, and so the wood is available, and stays sound in the heart for quite a while after the tree dies.
I have seen elm timbers twist and bow, so you may need a few extra, but that would be normal enough.
I used an elm timber (9x9x24) as a tie beam in a house around 15 years ago, it has less checking than the oak or maple timbers around it....
cutting the joints will be tough, even green....