First IMO if you do that you have a code violation.
Throughout this Code, the voltage considered shall be that at which the circuit operates. The voltage rating of electrical equipment shall not be less than the nominal voltage of a circuit to which it is connected.
Along with that it is a bit high, + or - 10% is about as much as you should push it.
208 + 10% = 229.
240 is little more than 15% high.
I would look into getting a pair of small bucking transformers.