I am engaged in a small claims court bench trial in November against a contractor that low balled a contract offer.

I assume from your facts that there was a hearing before magistrate, and the loser of that requested judge trial. Curious of result of that... Also assuming the contractor is Plaintiff suing you for balance, a very important issue can be licensing. IF the work done required a builders license (and there are numerous things that don't) AND if he or his company was not licensed, suit should be dismissed. You can verify that on line at DLEG website. Some older contractors incorporate or set up LLC, but don't understand the company has to have its own separate builders license, so even if owner of company has license, case should b dismissed if company is the Plaintiff and no license. Finally, don't depend on lack of written change order to defend against additional charge if there actually changes ie upgrades to original deal. In small claims court judge has a lot of latitude to do what's right Definitely take any witnesses you need- can't hurt. Good Luck!