I realize that the car guys do this all the time. But worrying about this has more to do with just reduced range on the transmitter. The bigger picture is that it could get the user in trouble with the FCC. All of the frequencies we use are sandwiched between frequencies used for commercial purposes. If a RC user chances his crystal without retuning and it bleeds over on the commercial frequencies that user could face very steep fines from the FCC.

Ken