Note- I had the 944 ultra low shocks- so, with the 11.5 inch shock there are going to be obvious differences from the regular, inch higher shocks.
I had the 944 low shocks on my bike. For me, even at a half-inch shorter than stock, the shocks were an improvement over the stock SGS hand-adjustable shocks.
However, a buddy of mine, who occassionally rides two-up called progressive to get their advice. Progressive advised him that he would find the regular and the HD options on the 944 Low, simply too uncomfortable because of the reduced bottom end travel. The regular (not low) version would have been good for his weight and riding style, but would not have solved his vertical reach challenge.
If you are on the fence, I recommend calling Progressive directly. Tell them what you are looking to purchase, tell them what you are hoping to get out of the shocks, and explain your riding requirements (light-weight rider, often two-up, etc). They were very helpful when I made my purhase, and they were completely honest and transperant when my buddy called (even though it cost them a sale).
They don't sell direct to the public so you don't need to worry about getting hooked in to a sales pitch on the spot.
Good luck.