I haven't tried a Rico Royal Graftonite on soprano. I like the piece on tenor and baritone though. They're actually better than many pieces costing 5 times as much in my opinion. On Soprano, I use a Meyer 5M hard rubber piece, which sounds really good on my Keilwerth.

I use a Meyer 5 on my tenor which I like very much but one thing that I find with the Cannonball mpc is that it's tough to blow. I'm very new to the soprano so maybe this is what I should expect especially if I want to keep it in tune but do you think the Meyer 5 for soprano will be easier than the Cannonball? Perhaps not a fair question since there's really no way to compare facings sizes since the number system for mpc's aren't relative to each other but the CBall mpc I have is labeled a "7."

The facing is what really makes a difference. The CBall mouthpiece is probably more open at the tip. Try a softer reed with it, like a #2 and that should make a difference. I use a 2 1/2 with my Meyer.