CAPI for Z-Wave thermostats

I read several posts about controlling my Z-Wave thermostats, and tried two approaches:

1.
hs.CAPIControlHandler(hs.CAPIGetSingleControl(306,true ,"68",false,true))

2.
hs.SetDeviceValueByName("My Thermostat", "68")
hs.SetDeviceStringByName("My Thermostat", "68", True)

While either solution seems to work initially (Status and Value both change on the Device List page), once the thermostats are polled, the (unchanged) values from the thermostat device are read and my values disappear...

Not sure if this is important, but I use CT100 thermostats.

And FYI - I can set the setpoints and modes just fine from the Device List page, but I also need to set them via scripts (e.g. it changes when the alarm is set on or off),

Any ideas/suggestions?

Thanks so much!