Is the axis of light anything like the Axis of Evil, Geroge Bush is talking about? Sorry couldnt resist.
To be honest, I dont know the technical answer to your question, but a lot of projectors are setup with the projector higher because of personal and projector requirements. They dont directly project head on and they dont to have a problem.
I just talked to technical support at Stewart and they think it will be fine. But again since I dont know the specifics of how much higher and what kind of angling you are going to be doing, something extreme could make a difference. He said that the off axis comes more into play if the light or the projector image is coming in from the sides.
He told me that the Runco 500 (i think, I just blanked on the number) can be used to project from really weird angles of the room. The Firehawk could not handle that