Okay first I will say that I don’t think 8 315s match up to 5 1ks as far as yield goes (I guess depends on your yield from hps) and I also don’t think think they cover a 4 foot width either(unless part of your room is walkway). You room is just ackward shape/size for 315s to cover it all properly.
Your watts have been cut back so much That if it was me and I could afford it and cool it I’d use 10 in that space hung side by side at 4 foot centers with the bulbs orientation running the same as long wall of room. closer to the walls than center(walls must be reflective for that to work right, Mylar is cheap).
That being said cmh is great I love it but I don’t buy the hype that you can run them so soft (far apart).
Disclaimer: I run way too much light per sq ft according to every hydro shop worker and friend I know. Its bullshit tho it’s like saying 2 600s is enough for a 4x8, but look at yields grown that way.