The mannable ack on V-bases and fields has about a 4k range I think. That's 4000 yards or so, about 12,000 feet.
Ostwinds have a horizontal range of about 2.4k and are pretty effective on PT boats, where you can see the splashes and adjust aim. Range is about 2k vertically, 2000 yards or 6000 feet.
A good bombing altitude is around 18k, 18,000 feet. Remember, icon alt is measured in meters (yards) and dial gauge is in feet.
Les