Building a DIY Flowering Light - 100W COBs and 3W LEDs

Hello all. First time posting here, though been lurking and learning for a good while.

Just starting growing again after a few years off, and I want to go as cost-efficient as possible, and as I'm not a fossil, LED appeals to me and is the way I want to go.

I've designed a reasonably low cost, but hopefully effective LED lighting system (total cost about $350) based around the following parts list:

Emitters
6 x 100W COBs (Cheap chinese ones)
42 x 3w LEDs (30 x 640-660nm Deep Red, 5 x 620-630nm Bright Red, 4 x 460-470nm Bright Blue, 3 x 440-450nm Royal Blue)

Drivers
6 x 100W Cob Drivers
7 x 20W Drivers for the 3W LEDs

Cooling
5 x 300x140x20mm heatsinks
6 x 120mm computer case fans
2 x 4-channel fan controllers

Hardware
3m x 50mm Cable Tray
2m x 2.5mm Mains Flex 3-core
3m x 1.5mm Mains Flex 2-core
Nuts, bolts, hangers, cable ties, heat shrink, junction boxes, mains plugs, etc.

This is my first ever build. I'm splitting the circuits into 4 so that I can disable certain banks of lights by just turning off at the socket.

I've worked with electronics a fair bit on a hobbyist level, but never worked with high powered LEDs and certainly not drivers... I've put together the sketches below of my proposed design (total footprint 1m x 0.3m), and was wondering if anyone has any advice or ways to improve this. My room is 4' x 3'.

I use 9 vero 29's. 3 5k and 6 3k. I came from 3w diodes and chinese cobs. I have a pile from the last 4 years. A month ago was my first harvest with the new lights. Solid rock hard SLH and SSH buds. Others here are using far reds etc. I'm sure it makes a difference. But or me this is just to easy.

I don't mean to burst your bubble but why are you set on LED? Since your goals are cheap and efficient, LEDs are currently not able to meet those two requirements. A HPS, IMO would be best suited here(if you want to stick to a $350 budget for 12sqft) .

Sounds close to what I did for my reef tank. These guys have been great here to talk about COBs and know their stuff... Mines (4) Cree 3070's with a ton of Royal Blues... The COBs still overpower the Royal Blues easily. I have to dim the 3070's like crazy to get it to the 12k look but I'm hoping growth will be much improved while I'm not looking at the tank and leave them at full strength.

If you use high quality red/blue emitters, the cost is quite a bit higher than COBs, the labor is a lot higher and it is more work to lens them. So if you were looking for the cheapest COBs, that would be either Veros run very hard or generic COBs run very soft. I think the Veros are a better bet because generic COBs are not as robust and you may find many duds that are damaged before you even use them.

All that said Draz is right, once you are in that arena HPS and CMH lamps are competitive with low effficiency LED. That is especially true with the HID improvements (1000W DE HPS and CMH)

Another way to look at it, the assembly, heatsinks, drivers, labor and cost is expensive. So if you put up all that cost and potential, but skimped on the emitters, it would be like putting an old kia motor in an expensive race car chassis.