Hey Keno, before you decide anything, look at Garaulds thread in vendors, I believe.
He makes a really cool rack that incorporates a backrest. I bought one. It's SO much better than a topcase. He made the rest removable, so if I ride solo, I can take it off and still have a rack. With the rest on, my wife or son has a nice backrest to lean on. There is so much different luggage out there that can be strapped on, I didn't want to limit myself to what I could carry in a topcase and side bags. And the rack gives you a larger platform than the stock rack. I'm still trying to make your ride next week. You can look at mine, or look at all the pics on the thread, and have him fill your specific needs. I found things from three different racks that I liked, and he was able to incorporate all of them into mine. The paint is a great match, and if you have a specific back rest in mind, he can work that out also.
And Gary, if you are reading this, I'm sorry I haven't posted pics yet. I don't even have a good excuse. I hope this rave makes up for it a little.
Ride safe.
Bob