Thanks for the suggestion - that’s what I originally had in my code, but I’ve been having a hard time getting a plain vector of static vectors to play nice with adaptive ODE integrators. Guided by discussion ODE of Vector of Matrices I decided to try out VectorOfArray.
If I were doing this in MATLAB, I would simply store them as a matrix (each column one particle), but I’m trying to “stretch” myself and try out other ways that (at least to me) appear more julian.