As a first rule of thumb, we always recommend that you install your Spiios in the middle of your rootzone for both greens, tees and fairways.
The Spiio is two inches wide and the soil moisture probe starts about half an inch below the top of the Spiio. Practically, this means that if you want data from, say, a two inch depth, then you need to install your Spiio one inch below the turf thatch.