My first attempt at a forest planting using 7 BC trees I bought for $3.50 each 3-4 years ago. The hardest part was trimming the large root systems to ~4" deep so they would fit in the 16"x13"x2" mica pot. The tallest tree is 34" and I will add some moss in a few days.
Unfortunately this was the largest pot I had on hand and really needed to reduce the number of BC I have laying around. I had to prune the vertical growth & trim the roots pretty hard, so this is more of an experiment as to what a BC can take and survive.
Pot's too small. Trees mostly too tall and not close enough together.
I stole this photo from an old post by Redwood Ryan (forgive me) --the trees are BC (needs a repot), Notice how close the trees are together. Those trees started out the same size as yours many years ago. The owner drastically pruned the root masses to fit together while the trees were young. That selective drastic root prune allowed them to get the trees placed more tightly together. BC can take that kind of thing, provided you keep the soil moist.