A lot of it depends on the judge. Some judges will go "Oops! He obviously has blue eyes and the ticket says green! Dismissed!", and others will go (and this is documented) "Because the officer took the trouble to write up the ticket, you must be guilty." Obviously the latter was thrown out on appeal, but the fact still remains that the judge's personality has a lot to do with guilty verdicts regardless of whatever facts can be brought to bear in a trial.
Check to make sure the state law doesn't have something to say about how often the device must be calibrated. Furthermore, demand to see a repair manual for the radar gun. It will tell you a lot about it that you might find useful. Was it a Stalker Dual, by any chance? Those are like the only ones they use in NY now, and they have a +/- 2mph margin of error. It doesn't look like it'll help in your case since it's still 11mph over the limit, but every little bit helps.
Make sure you know what you're entitled to under the law of the state and make it stick. If the judge doesn't allow it or the DA refuses any of it you have grounds for an appeal if you get convicted. Also, make sure you have a multi-pronged approach if you can, just in case you get shot down on one approach.

