I've got an 05 rocket, got my backrest and rack with hard saddlebags, don't like to run a windshield at all, I had it at 135 the other day, stable as a rock.
but I noticed on my honda shadow that when I have a load on the rear of the bike, and put on the throttle lock, let go of the bars, that I would get wobble. the more weight on the back, the lower the speed at which it would wobble.
no cargo in the bags, = no wobble.
how much rear weight do you have? I agree about the tall windshields not being good for high speed. However, on my recent run up to wyoming, I hit 130 in nebraska with 2 loaded saddlebags, and my ugly milkcrate 3rd 'bag' behind my backrest full as well, and running a tall windshield, I still had no wobble.
but my bike does pull slightly to the left. don't forget about wind.. sometimes it pulls slightly to the right, and mostly it doesn't pull at all.