How do you create an TDM implicit channel.

How do you create a TDM file with an implicit channel using CVI? What properties do you have to set to get an implicit channel? The "representation" property is read-only, so I cannot set it to implicit_linear. So far I have

status = DDC_AddChannel(channelGroupHandle, DDC_Double, "DateTime", "Linear Time", "s", &channelHandle);
status = DDC_CreateChannelProperty(channelHandle, "implicit_start", DDC_Double, 53431389753.546461);
status = DDC_CreateChannelProperty(channelHandle, "implicit_increment", DDC_Double, intervalSeconds);
status = DDC_CreateChannelProperty(channelHandle, "length", DDC_Int32, nPts);
status = DDC_CreateChannelProperty(channelHandle, "lengthmax", DDC_Int32, nPts);
status = DDC_CreateChannelProperty(channelHandle, "monotony", DDC_String, "increasing");
status = DDC_CreateChannelProperty(channelHandle, "displaytype", DDC_String, "time");