There’s no HAIL sensor: what Tempest does (from what I read), is that it uses the rain sensor + the haptic sensor to distinguish between heavy rain and hail. I don’t know how accurate that is and if it’s fully implemented. You would have to try. 
Well, in case I try to simulate hail at home.
For the rest, does the device work well? Is it accurate?
Better than general weather sites.
You can check some of my weather station sites, I wrote you a DM with the links.