I think it will also depend on how you are going to age it and how you will bottle it.
I wouldn't plan on adding enough sugar to hit 9% and then expect the yeast to die off. If you shoot for an OG to hit 9%, murphy's law says the yeast will just eat it all dry. If you add fermentable sugars to hit 15%, then it might be so high that it stalls or STILL goes dry. You never know with a fruit must.
You could try racking and cold crashing at your target gravity. But then you would need to decide how you are going to bottle it. There's a lot of variables that might cause bombs unless you pasteurize if carbing or use sorbate if drinking still.