Hoppy, you've got a solid design-I wouldn't lose any sleep over the PAR level variations. Plants seem to be pretty adaptable to varying amounts of light from what I've seen in my own tank. I've got JAVA FERN that is thriving, and is growing directly under my led rig. The ferns are only 10" down from the lights, and a complete carpet of Glossostigma is spreading like crazy at the substrate 34" down. According to every aquatic plant book that I've ever read, this should not be possible. I guess- no one ever told my ferns about their low light requirements, HeHeHe.