Ah boy take this with a grain of salt, but I have two soprano mouthpieces. Both are Selmer S80's, one a C* and the other a G. Yeah a G facing. Its crazy open, but since my main chops are alto I find it easier to control with a harder reed.
On base with your Dukoff 6* on alto, I know that if I put a slab of reed on my S80 G the sound will be pure and smooth, perfect for a classical setting. If I choose the Hemke 2 1/2, however, the thing screams and gets a really nice edge.
It would be my reccomendation.