if it need to retain coverage footprint -- dim it, if possible. Height changes footprint, so consider that and make sure it covers everything sufficiently when moving closer. Farther away just makes it more evenly spread out, typically.
inverse square law -- every 1' you raise it that is 1/4th the intensity of light per sq. ft *or any unchanging area of comparison.
Chage your perspective a bit on how to fill an area.. height varies. Stretch varies, but you can start with a guesstimate of 2x the size. When it is roughly 2/3rds of your Length and Width, you'll be roughly 1/2 size (70%*70%=49%)