I use one custom turret for everything from 900' to 11,000' and haven't had a issue. The turret is set for 5,000'. While I think having 2 turrets can be useful, it dosen't appear to make much of a difference when you split the difference at 5,000'
I'm planning to have a tarp with me and using it when concerned about weather.
The Borah website appears to be having issues. It isn't showing the options described in the thread