I can't answer what the actual dimensions of the '98 stock shield are, and I think there are a few different versions that are different sizes from what I've seen (with and without cats eyes, etc). I knew when I cut that shield down a little that it was taller than stock, even after cutting it. There was a bit more buffeting around the sides of shield before I cut it also. I thought of adding "wings" but never got around to doing that.
Wind at shoulders is likely not all from the shield but coming up from under and over the mirrors and pulling in due to the bubble of vacuum that exists directly behind the shield. My old GL1500 (Gold Wing) had a terrible shield on it from the PO that caused a massive vacuum bubble and resulted in a lot of buffeting for me and passenger. I did replace that one with a taller shield but it was a combination of a more aerodynamic shield (not necessarily taller or bigger) AND side fairing deflectors that did the trick on that bike. I would think the same here. Those "wings" should help out a lot and I would see what they do for you before going too far into paying for more shield... when the weather warms up. Then if the wings don't do enough look closely into where that wind is coming from. Keep in mind that the more you deflect the wind around you, the bigger the calm bubble is and also the more the wind slams back in from behind hitting your back. There does need to be some venting at the shield to relieve some of that vacuum and manage that. The ST does have some venting so that is good.
Deflecting the wind from hitting you will reduce the noise as well. But much of the noise is due to the helmet itself (some are just noisier than others). Wearing ear plugs on the highway reduces a lot of wind noise, and a quieter helmet reduces it even more in combination. I don't remember if you said earlier if you wear ear plugs.
) and they help. The 3/4 face helmet is not so bad. And without the face shield is even better, but I'm not riding without face shield anymore. Full face helmet I have is one of the cheapest ones (I got from friend for free, he didn't use it) and it's horrible, but I had to wear it over winter - it's too cold for 3/4 face helmet.