I respectfully disagree. People generally use side lights because they either didn’t have adequate overhead lighting to begin with or they overgrow their space. Or there’s always the guys who see others doing it and figure it’s a great idea so they jump on the bandwagon. In most scenarios it will help their yeild, but probably not as effectively as investing that money elsewhere. Outside of running a scrog or sog you’re always going to have some buds developed more than others. Side lighting may improve that a little, but it doesn’t make it go away.
You’re correct about the law of inverse square, but adding reflectors doesn’t solve that. If at 12” your at saturation level and use a reflector to create a more intense beam of light, all you’ve done is raised the gap to meet the saturation level right? So you choose between having a more intense light but running it higher, or more spread light and running lower. The biggest difference is that running without a reflector doesn’t cost you any photons, using one will.
If he was short on light a reflector would help, absolutely. But I don’t feel they’re needed or good for this application. There are lenses available for the boards that essentially do the same thing. But they are best for th guys that want cover every square inch of their grow with the boards and run them at 40 watts. The one downfall he has is the end to end heatsink as opposed to a side by side. But that was strictly because it’s what was available at the time. Getting them side by side will get the coverage more even, otherwise I think he’ll be golden.