permnoob:
also since that is a pretty big solenoid, throw a low ohm resistor behind your flywheel diode, this lets the resistor dump the power instead of the diode. google info on it, but I think a 1ohm or so would be a nice number. I dont remember, it was a wihle ago I needed to look up some stuff like that.
Most of the flyback energy gets dumped in the resistance of the solenoid winding, not in the diode. The main benefit of putting a resistor in series with the diode is that, if the resistance is comparable with or larger than the DC resistance of the solenoid, adding the resistor speeds up the current decay in the solenoid, which may be important in some applications. However, adding a resistor also increases the peak voltage applied to whatever device is turning off the solenoid.