TPS40210 how does it respond under a no load condition in a flyback converter

I was looking into designing a 3 Watt DCM flyback converter with the TPS40210 with multiple outputs and I need to understand what the part will do under a no load condition, given the minimum duty cycle of ~5% at a switching frequency of just 200 KHz. I expect the voltage would increase, but by how much? Can a zener clamp be effectively employed to keep the voltage from becoming too excessive? Would I need to clamp all outputs or would clamping just one suffice? I don't think the clamp would be needed if the increase in voltage is less than 10%. Any other suggestions would be helpful and appreciated to increase my understanding of the part's functionality.