Because of their spacing I'd guess less than 4 but you should ask them how many in a 2x3 space. The commercial Undercurrent may not be the best choice since they don't use remote reservoirs/controllers...then again maybe they'd custom design something for you.

I'm gonna build my own system with a remote reservoir and controller. Hydro is going to be a lot more work than soil but I hope the increase in harvested weight will be worth the effort.
I have made some pills from my white widow they are "0" size and I took one last night and I was trippin for a good two hours before I could even start to maintain. I smoked a joint of GDP with two of my buddies and stayed stoned for a good 4 hours. Whit all of the strains I've grown I've found them all to be very potent. I think it's a result of the LEDs they are working flawlessly for me now is the time to work on yield I've got the basics down for soil, hydro will be a challenge I think I'm ready time will tell.
One last thing cannabis is working to help my wife with IBS long term we hope to cure it for now it is being controlled.

If you're building it yourself, you could go with one 3x2 bucket/tote with 5 or 6 holes cut on top or you could do the plumbing for individual buckets (again 4-6).

I find hydro to be less work once you get it going.

Looks great good job, If your doing hydro the trick is to not let any light in the res, and keep the water temps in the hi 60's low low low 70's.
If you run co2 make sure your air pumps is in a separate room, you don't want to pump co2 into your water. Also no organic, you don't want live culture in your water. Under current systems are great, the ph and nutes levels are consistence from container to container. I really like advance nutrients, works wonders for me, expensive though.


good luck