Watermelon Mint Sorbet

It might be more fair to think of this as a Mint Watermelon Sorbet - the mint flavor was dominant, almost overpowering, in my attempt.

Two things come to mind on that point. First, I scaled the recipe up by three to try and use up a watermelon which was far larger than necessary for a small Fourth of July party. Maybe mint doesn't scale linearly. (Though since I also find it a little too sugary-sweet, I think that's not the whole problem.) Also, I was using chocolate mint from my garden, and though I aimed for younger leaves, certainly some more mature leaves got in there as well. I have no idea how to control for the strength of your mint crop, but I suspect that's an issue too. I'd love any tips people have (or any other experiences with this recipe).