My emerald mainblade is nice and bright, and so are my sides, and i just run filters to them. I wonder if I should just stick with :/ the endless options of the diamond are very cool though. Maybe its best left for a single blade.
Did you try different colors? If you're using a color that only features 1 LED, it's not going to be as bright as multiple LEDs (at least I assume so). So, Orange will be brighter than Red and so on. If you can add white, that will make it brighter... though, also whiter (which turns Red into Pink - probably not what you're going for - but looks nice in Blue).