You can shorten the display URL to fit in the 35 characters (and it still must contain the .tld extension). You also might have to file an exception request with Google since your display and destination URL do not match.
When choosing a shorter version of the URL, you cannot choose one that looks like another website that consumer's will recognize (which is up to interpretation).
The best thing to do is either call Google or contact them within your account and explain the situation and state the URL you would like to use.
I thought there was a help file on Google's site about this but can't find it at the moment.
Msg#: 3888749 posted 10:04 am on Apr 10, 2009 (gmt 0)
But in case i crop my url into something with a tld extension, Google is accepting it as correct and is not showing me the exception request area. Also, Google says that the cropped url should have an existence in the server.
Hence, I had to do away with the www and the .com extension. That way the url come to exact 35 characters. I have also filed an exception request for this.