Your 1ks and spacing are perfect.
So much more cost in 6s.
They do not penetrate nearly as deeply in a canopy.
Your cola that grows will be better quality and bigger with 1ks.
The 6s will only penetrate so far in the canopy and still produce premium material.
Maybe penetrate 12", maybe less.
So the amount of 'bearing surface' on the stick, the length of the stem on which bud will grow, is substantially greater with 1ks.
The length of the arc tube in a lamp has a lot to do with performance.
Point source vs line source and all (1k more like line source than 6, carries a disproportionate gain)
Do planters like Mississip hip, trellis them with a screen 12" above medium, get a screen of horticultural trellis 6-12" above metal screen. Colas want to fall, they will stay put via the horti trellis. Helps so much with light exposure, quality, yield.
Put a reflective surface at top of medium. Affix reflectix in walkways, so you have a continuous reflective floor. But only when plants are thick enough to handle the light.
Arrange whatever reflectors so that they crosslight the neighboring 4' wide bay perfectly. Multiple overhead 1ks spaced like that beats 6s all day long.
Lower initial cost as well, lower relamping cost, less cords in the way.
I have run 6s and 1ks in vert and overhead. I am only willing to run 1ks overhead, based on experience.
But 6s in cool tubes, vert in between the rows, shining on the sides and bottoms of the plants, bouncing off the reflective floor, chunking up the sides and bottoms so that you get more premium material and less popcorn, sounds fun to me.
And the only time I would consider ever using a 600 watt lamp.
600s do not produce any meaningful advantage vs 1ks.
600s do not in fact produce more lumens per watt, not with a good lamp choice. 155k lumens for digilux 1k
[email protected] amps. 95k for digilux 600watt
[email protected] amps. Yes I like digilux for the price, spectrum, and brightness. Plantlightinghydroponics has them for like $60 with shipping, let us know if you can find them cheaper elsewhere.
You can get them closer because of less heat, but you could just get a 1k and back it up some, and get the same light values at top of canopy, and much better penetration through the canopy.
I will state again that crosslighting the neighboring bay with 1ks is the way to go.
If you have room on your circuit(you will if you have digital 1k ballasts) then you could fill up the extra room on your circuit with dual 600watt ballasts from Lumatek.
Then put them in the aisles like I described.
Hopefully you will be doing chow dtw, all the cool kids are doing it. High performance, high reliability.
I even show a nute formula in a thread for chow dtw that I make from 5 50 lb bags of fertilizer salts + micros that I bought for 181.06. It will last me 5-10,000 gallons depending.
For the love of all that is good in this world, get 1ks. I say this from years of experience with both. 6s only look good if you have not worked with 1ks yet.