Hopefully this works correctly on my production blog the first try LOL.
Update: It Worked! http://mhurl.com/1 links to this post now. The Longurl.org website and DestroyTwitter Twitter client are able to preview the link without any problem. TweetDeck v0.26.1 and TwitterFox 1.8.1 are not able to.
I modified the WordPress Twitter-Tools plug-in to create the short-urls using my shortener before sending the tweet out about the post.