I bought a set off Progressive 412 rear springs on eBay on the cheap ($60) and tried them for grins. They are 11.5". The middle spacer kit fit our bikes, so installation was non issue.
My impression is that the spring rates are stiffer, but the rest is the same. I'm running them on the lowest preload, and they are very comfortable, a noticeable improvement over stock, do not bottom out, and ride and handle very well. I weigh 210 and carry up to 30lbs at any given time with gym bags, computers, and lunch. I'll keep my eye open for the correct rate springs on eBay, but I'm happy with them. My only desire is that a softer rid could be dialed in for a highway trip. Otherwise, I'd have them at this setting- whether it were the lightest, middle or stiffest.
I've drug the kickstand once, but I was trying to bottom something out. I wanted to know where the limit was intentionally, instead of mid turn somewhere when I didn't expect it.