Only thing I can give is, Moving them up or down, or forward or rearward, will not have as much effect on them as moving them to far from side to side.
If the 6 or 7 ft. is forward or rearward, I don't think that is to much. To left or right may give some drifting, Unless you place them in the same order and about the same distance apart.
The only problem I can see is either to quick of a landing or a little late.
Kinda like shifting the runway at the airport.