I had the same issue with A-10's in WoI, but from the opposite perspective, too high!
The SAM's are ferocious in Syria, and here's my wingie diddy-boppin' at 10,000'! >Pop< goes the warthog!
As to altitudes, I think they are adjustable by skill under AI somewhere. But, be aware, it applies to ALL AI, as in enemy too.
Wish there was a separate area for friendly and enemy to adjust to taste.
Anyway, the specific file eludes me at the moment, as I am not home where my SFP1E files are. I have to put them on my work laptop, as I have WoI here.
Let me rummage, if no one gets back to you, maybe I will have found it.