This could of course be, but I thought it was quite the opposite, that the U87 style headbasket was designed to reduce reflections and resonances. Indeed the M71/UM70 headbasket is designed around a similar shape, and the (very rare) Neumann U497 was literally a K47 in a U67 body.
Are you sure it wasn't a question of what height you had it in the headbasket, or that you rather WANT the resonance that a U47 style headbasket produces?
First of all, it is about the size of the headbasket, the internal volume. By analogy, the same speaker mounted in enclosures of different sizes will have different resonance frequencies.
Then form the headbasket, with parallel or inclined, flat or curved faces, etc.,
the shape, the density of the grills, meshes, the number of layers,
the position of the capsule inside the headbasket, height and inclination (NT1-a has an inclined capsule),
the dimensions and materials of the mounting support, more rigid or elastic materials,all interior materials, glossy or matte
Etc etc
I like to do sometimes absurd experiments, which often defy electronic theory, physics, acoustics, etc
I didn't aim to achieve a specific sound, I just experimented and reported my observations, maybe it helps someone.
For a long time I stopped looking to make historically correct clones, to achieve a certain sound.
I just do what I like, how I like.
Often you find what you need in a completely different place than what you are looking for.