i would not attemp any reports until late June into early July when temps are warm and the tree can be kept outside to recover.
I honestly think you might do an angle change without need of an air layer. But...people do cuttings with these of grand thickness with success. But I would imagine you could tilt the tree with no large hiccup.
Here was my angle change. Quite honestly...I can't make much of your tree...you have photos pretty much looking down on it. You need to take a photo from straight on looking at it as I have here for one to totally grasp the look of your tree. Would like to see all four sides like that from your original planting. You may have something there you don't see. Or...it may do good with an angle change. But your current plan makes the leader seem...so straight. The original planting it seems it's at an angle. Which gives it some character. I just am curious if there isn't more options your not seeing.
Bougies make a great project...fun material...hardy plant. You will surely have fun with yours!
From this...
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