@Randomblame and others, I have 20 Bridgelux 1ft strips and 6 - 2 footers and I have an HLG 185H-C1050A and HLG 185H-C1400A to try and build something suitable for the cabinet in this thread:
https://www.rollitup.org/t/new-cabinet-build.968904/page-2#post-14377145 There are some major height restrictions and about 4 sq. ft.
Hmm! For only 4sft you need only one of these 200w drivers and you already get 50w/sft. That's a lot! Probably +1000μMol/s/m². Do you want to use all the strips to make it as efficient as possible or do you need a few for a second veg area? You could use the HLG-185H-C1050 and 18 1footers in 9s2p(2x 9 strips in series connected in parallel). Each strip would run at 20v/525mA and you still don't need heatsinks. Only a frame, u-channels or alu flashing/alu sheet to mount the strips on.
It's not so easy to use both typs of strips on the same driver because they both have the same voltage but different currents. Diodes on 2ft strips would run with half the current compared to the diodes on 1ft strips when connected in series. You need to use 2 1ft strips in parallel connected to one 2ft strip in series to get even brightness. A circuit could look like this:
But it's a lot of wiring effort because the strips would be mounted in a different way and you need a lot of wires to create the circuit.
18x 1 foot strips in 9s2p is a lot easier and you can use the 2 footers for another light/project.
Hate to say that but if you would have asked earlier... you could have ordered two HLG-100H-20A or B's for parallel connections. One for the 12x 1ft strips and the 2nd driver for 6x 2ft strips.
Is it possible to send them back and choose other drivers? 400w is anyway much to much. For 4ft² you could get away with only 150w (37,5w/sft)and still get ~750-800μMol/s/m². Maybe two HLG-80H-CxxxB would be already sufficient, one with 350mA(10x 1ft strips in series) and one with 700mA (5x 2ft. strips in series). Would be ~180w and an HLG-80 costs only 35$, HLG-100H-20A probably 36$.