Howdy Ralph,
Perhaps this is where you could use the "sharp" convention for the pseudo-pitches to your advantage.
Using the example of placing the rhythm indicating drum notes on "A", the "naturals" would be the "x" notehead, and sharps would be the "triangle" notehead. It's not a diamond, but at least it's different than the "x." Might that work for a workaround? I just tested it, and it works mechanically, I'm mostly asking if it works for real musicians
ttfn,
Sherry