IMHO, they don't bring enough to the table to justify
I will strongly disagree with this statement. Only because the benefits I have received from using them. The LS strain I've had going for the last I don't know how many months are soaking up that 660nm light like a sponge. I've tried the 630nm light with the LS and it doesn't even touch the benefits I've gotten from the 660nm wavelength.
I don't know how you are using the 660nm, but I wanted to say to not disregard the 660nm just because they haven't worked quite right for you, which could be due to the "other colors" you have chosen to run side by side with the 660nm.
I'm not "at one" with the english language right now so bare with me a little bit. LOL
The point I'm trying to make is for example, just because the 660nm doesn't seem to work well with your strains, which last time I was aware you were growing Indicas and they like a more red heavy spectrum. The 630nm work better for Indicas I think because they push the red spectrum "harder" than the 660nm in available photonic energy whereas the 660nm push photosynthesis more. What I'm trying to say is the 630nm wavelength will shift the overall color of the light to the red side more than the 660nm giving your Indica's a "redder" spectrum using fewer lamps, BUT, the 660nm will drive photosynthesis better than 630nm and still keep a "blue heavy" spectrum that Sativa's like such as my LS(Lemon Skunk).
I know this is probably confusing for you and everyone else so take it easy on me after I post this. I can try to clarify later, but to simplify, 630nm DOES work very well with Indica's because they love a red heavy color spectrum. I ask you to try using 660nm lamps and create a blue heavy spectrum and try some Sativa's. You will see what I'm getting at.
I don't think there is a point in using the 660nm with Indica's when using T5's. Led's will be a different story because you can fine tune the spectrum with using many more light sources. When you only have 4 to 8 slots open in a T5 fixture, lamp choice becomes extremely delicate.
I will tell you what has been working quite well for me in the T5 world for Sativa's. Blue/660nm/Blue/660nm. Adding a Florasun or 2 in there has really boosted shit due to the completion of the spectrum perhaps, but either way I've tried to use 630nm redsuns and the redsuns just don't do shit compared to the 660nm for the Lemon Skunk.
630nm will push the red spectrum for your fixture, but 660nm will push photosynthesis harder, but if you don't get the balance of light color to the red side for an Indica you will see weaker growth. Not sure if my Sour diesels are Indica dominant, but they don't like the 660nm/blue/660nm/blue with or without Florasuns because they prefer a yellow/red/orange dominant spectrum and prefer MH hortilux blue which is mostly yellow/green/orange and that 630nm color you like so much. The Sour diesels do very well under the MH hortilux blue but don't do well under the T5's unless i throw in some 630 like the coralife 6500k whatever the fuck they are called that have a lot of 630nm and orange/yellow/green in them.
Fuck, I know I'm not putting the words together well, but I'm really sucking right now. A big fat F for me in my compositional drafting. LMAO