From what I understand, the soil type only affects how often the Rachio will run water/soak cycles. You can then go in and change the default available water. I needed my lawn to run more soak cycles so I chose clay soil type, then lowered available water to the correct value. So, like you suggested, I would start with 0.17, and keep an eye on the lawn to be sure the water amount is correct over the next few weeks. Don’t worry too much about soil type, available water is the important value.