Indeed. Let the plant grow a bit more, and ensure it is strong: A cut-back will be more effective.
Is this the only one of the species you have? Do you know how well they backbud & close cuts? This will determine how much you can let this grow. I suspect these can grow very strong when healthy and well-watered.
The style is a great one, as this is -afaik- the natural shape these trees take in savannahs. I think that you will have to prune the branch growing into the canopy, and take it off, or create space in the canopy so that it can fill its own space. This style is hard to create a realistic looking tree, and not end up with a topiary plant. As far as I understand it, each section of the canopy is growing out of an individual main branch. So the canopy is effectively a compilation of individual mini-canopies on a branch (Much like styling a juniperus pad, as shown by bonsai4me.com at
bonsai4me.com/Images/AT%20Shaping%20Juni...20branches%20(5).JPG, below, but vertical and 3d of course).
I am not sure your plant is big enough to pull it off. I would aim for a bigger trunk.
This is a nice example, I find:
ibonsaiclub.forumotion.com/t16345-andre-...tyle-acacia-galpinii
i38.servimg.com/u/f38/17/27/55/53/pierne26.jpg