I would use the Build Waveform primitave. Feed the waveform in and set the t0 component.
I am not comfortable with the timestamp attributes. Both NI_ExpStartTimeStamp and NI_ExpTimeStamp describe the "time stamp of the first sample". So, what happens if they are set to different values? I have used set and get on other attributes with great sucess, but the timestamp attributes seem to be attempting to duplicate values that already exist elsewhere in the waveform.