Pointing Aiken Fa up in partCombine

[Benjamin Bruce]

Hello all,

I feel like there should be a simple answer to this question, but I can't figure it out.  I am using Lilypond 2.22.

My setup is Aiken shape notes, with two voices combined using partCombine. In one place, both the voices have the same note, which is a half-note Fa (right triangle). Since it is the same note, the output has two stems, one pointing up and one pointing down.

The issue is that the Fa triangle is arranged with one side stuck to the downward pointing stem, whereas I want that side to stick to the upward pointing stem. In other words, I want to rotate the notehead 180º.

Does that make sense? Thanks in advance for your help.

Benjamin Bruce