Small update, I just bought some Cortech Sport Saddlebags as a soft luggage option for now (the Givi hard boxes would be way too much $$ at the moment); the HR-4's arms are just the right place to loop the clips for the saddlebags. I haven't ridden with them yet though.
I also upped the shock preload by 1 more setting because I think there actually HAS been a handling change in the bike with a full tail box, it's just very subtle. There's a very little bit more weight in a high, rearward place that gets transferred around during turns, and I think it is noticeable.
I don't know what the shock preload might do, but I figured it was worth tweaking to see if it makes a difference.