I finally got around to making this lovely macaroni salad. I don't think I quite got it right. I put in a little more carrot than called for, and while it gave the macaroni salad lovely colour, I could tell that it was just too heavy in carrot. Also, I think the mayonnaise makes a difference. I used Miracle Whip, because that's what I had on hand, but it made the whole thing look too yellow. From my recollection, the salad was quite white, just as white as the Calrose rice typically featured in these plate lunches (as far as I can see). I think next time, I'll also use white pepper instead of black.
Hopefully I'll be able to recreate the magic that is Hawaiian-style macaroni salad. It is still the one dish I find I'm missing the most, believe it or not.
And no, I haven't tried making loco moco. That stuff is quite heavy. It probably would have done me well had I eaten that before going on that Diamond Head hike though!