Twitter automatically shortens urls, so the 117 character setting means that it will give you exactly the right length of tweet based on the length of your username.
There’s no way to give you more characters than my plugin gives you. 117 text characters + 23 characters for t.co length url = 140 characters. The plugin then subtracts the length of your username + 6 characters (the spaces count) for ” via @” plus 1 character for the ellipsis used to truncate the tweet text—the “…”
I’ve been asked about integrating bit.ly support or another link shortener, but haven’t had the time to make that happen. The only reason I can see that you’d need that is for tracking links, because as I said Twitter automatically routes all links through their t.co shortener.
I will look into how I may be able to implement that. Thanks for the suggestion!