Want to turn this into a shohin tree since the branching on the left side below the arrow is sparce. Doable?
I believe so. From what I can recall of elongating species they air layer better with a branch below them. And they may take longer to develop enough roots.
The question I would ask first is why are you thinking of air layering the top off? If it is purely because there are no branches on the one side could you make that side the front? The fact the trunk looks a similar thickness to your thumb suggests it’s already shonin sized.
I’m not trying to put you off doing the air layer, I’m curious about what you can see in the rest of the tree.
Just my 0.02 but that tree is adorable! I wouldn’t take the top off. Honestly, if you are unsatisfied with the design I think a lot could be done by letting it elongate and grow for a season with fertilizer to get it bushy and encourage back budding. This will give you more options for branching in the future and you could do a complete restyle in a year or two.
I would develop the branches on the left rather than air layer.
Have decided to hold off on the air layer.
So how do I force the energy/growth into the weak side of this tree?
Pinch/prune the strong parts and let the weak parts grow.
That’s pretty much it.