City pickers planter drilled out and being used as a traditional container. Just under 3 cu ft of potting mix. Two ichiban eggplants. Too many?
I think it'll be fine for those two.
I would have planted them on the diagonal, however.
I would plant up to 4 Ichiban in that container size.
3 cu-ft is almost 20 gallons an 5 gal/plnt should be enough. But considering the top growth 3 plants (staggered = in "V" formation) should be fine.