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How the heat pump interprets 24V signals is often hinted at in the heat pump’s manual. Lennox’s manuals, for instance, describe a sort of induced hysteresis mechanism where the heat pump ramps up gradually over time, rather than jumping to maximum. However, Durastar omits this information from their manuals.
First: “licensed HVAC contractor” is not a real requirement. Many states have no licensing program, so you are just as licensed as anyone else in, say, rural Indiana. The trick that folks in construction use is to simply lie and tell them you’re an HVAC installer.
The problem is that there is no standard for communicating thermostats. Instead, general-purpose thermostats have just a few binary 24V wires. They can ask for three levels (off, low, and high) of heat pump cooling, of heating, and of auxiliary heat. There’s no way to ask for 53% or 71% heat.