you dont have to be at 1,000ft AGL.
The bomb has to travel 1000ft. I like to run Bostons or Tu2s at 300ft AGL and level bomb. 300' of alt and over 300mph the bombs will travel 1,000' and boom! hanger destroyed or tank if you can figure out where you need to drop at. practice flying at 300' and 300mph+ then drop on a barn when it falls under your prop and see where you hit. then adjust as needed and there ya go.