Im going to offer some different advice so probably worth pointing out I dont have the same amount of experience others do.
I love the trunk line and don't see any reason to reset the tree's development timeline so heavily with a drastic reduction. You dont have any major bulges or inverse taper and you have branches in pretty great positions. The taper that you have here is not necessarily remarkable but its also not problematic and to me it does feel consistent with a deciduous tree. It's not the most hornbeam-esque trunkline but it still works very well as a general deciduous form and it will be very presentable when fully ramified. Building out the lower branches will over time create subtle taper from the bottom up as you develop most of your tree the areas with the most foliage mass will add more thickness from that point downward.
I would take what the tree is giving you and build what you can with the structure and primary branches you have. This will allow you to dive directly into the question of "how do I build secondary and tertiary branch ramification" which in my opinion it's harder to find material that is worth the time to learn how to answer that question. You can also start learning "how do i build an apex" which is also a very important and challenging skill and opportunity to dive right into that with this tree.
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edit - i meant to show the angle leaning even more into the direction of the trunk line and had the wrong angle at first
