I've seen rectifiers burn up to but since even going with 55 watts on hi and low side would actually decreases draw during hi beam usage mute point on zx14r. Even going to a 70 watt HID set up shouldn't cause any issues. The zx14r has some spare juice in there enough for decent heated gear.

The only thing I can see is getting a voltage spike back fed from the ballast "shouldn't happen if built properly" but to remedy this if that is the case install diodes in the source or positive connection. The coil and transformer should have them internally going across the primaries.