Here some stats from my last rides with the decoy:
1. 50.1km (31mi), 1.100m climbing, rest two bars battery (out of five bars)
2. 64.4km (40mi), 690m climbing, rest one bar battery
3. 34.2km(21mi), 800m climbing, rest two bars battery
4. 39km (24mi), 370m climbing, rest three bars battery
5...
Have a look at the SP Connect system with the micro steam mount.
I use this and it works great and holds the phone like hell (tested it on different down hill trails).
https://sp-connect.eu/collections/bike/products/micro-stem-mount-alu
I have bought a YT Decoy Pro Race as I was not willing to pay the premium price for the Specialized.
I have it now for 3 weeks and could not be happier about this choice.