Water depth changes how your light will refract. Yes depending on coral requirements light height is a factor. But generally we speak that of a standard depth tank, not a 7" deep water tray. Do any search on any brand light and most will have a picture that demonstrates light penetration at depth. This is why those people running 30" tall tanks need a 2g light, just to put enough light to get to the bottom.
put it this way my 90 gal has lights about 18" above and its around 24" deep. on my frag tank that is 6" deep with my ai sol (led) on the same setting as the 90 gal its about 30" away from surface and everything from sps to zoos seem to like it.
My 6" deep frag tank has a radion 12" above it and is fine. My 18" deep display has the lights 12" above. I am using wide angle lenses on both. The fixed mounting arms by ecotech for the radion put the fixtures 12" above the tank.
I think 12-14 inches is fine. I have the same fixture. Hanging about 12 inches on top of my 24x18x7 frags tank and corals are loving it or you can hang it higher and lowering the fixture down about an inch every two week.