I'm no where near these guys level yet and I could totally be wrong, so if I am my apology. I've been researching leds now for quite some time and I've yet to see any lm301b qb' in 3500k. I think the only way you're going to get that cct is if you go with strips. Why do you want 3500k any how? There is more blue spectrum in 3500k which is good for veg but for all around lighting I think not. With more blue in the spectrum you're going to get more of a stretch in your plants. Again, I could be wrong but from my reading and speaking with people here this has become my understanding.
Just get the qb 260 in 3000k and call it a day. You will not be disappointed! You can also upgrade your build as you go. Or go to digikey and get you some strips.
https://horticulturelightinggroup.com/products/260w-qb-v2-led-kit