Jeremy,
Is it possible for you to do a test 3" from the surface as well?
Overall great job!
As far as the comparison of Illumina and Radion also need to keep in mind that Radion consumes 50% more electricity! Having said that seems you only have a hot spot right under the light and the reflector reduces the spread by a great deal, so for an even spread on a 4' tank maybe 2 x 1' illumina should do better than 3 or 4 Radion!
Thoughts?
Also from your numbers with Radion does this mean you can see a spot light effect at 6" above the surface? hard to see from the pictures but a drop of almost 50% in light in 6" or less would suggest that!
I wish I was close eough to pay you a visit, but onceagain thanks for doing this.
Cheers,
Dave