The tree will keep growing proportionately. If you have big bulbous roots, they will also continue to grow. So the top half will continue to be out of proportion. It is not without a small amount of risk, but the best way to rectify this in "ginseng" ficus is to do a chop as per this thread:
Yet another Home Depot grab. Little ginseng ficus in 6” pot. Going to see if I can cut almost all of the tubes off and make a big cutting out of the top. Made the horizontal cut.soaked it in a rooting hormone slurry then potted it up in a coir/pumice mix.we will see.
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