After reading through this thread, decided to try this out for myself, as my 20" fixture from my old tank was not going to cut it on a 55.
Ordered Tuesday, shipped Wednesday, and evidently they tried to deliver to me Thursday. Went and picked it up today, expecting a package from the in-laws, not my light already!
Just going to try a single 300W over the 55 for now, if I pull the optics and still have too much shadowing on the edges, I will add something else. I wanted a light with a sunrise and sunset feature, but for this price, I am ok not having that.