Cherry-plum jam

It will be no surprise to me if, at this point, you accuse me of having gone overboard in the cherry-buying department. But I did so happily and am almost through my load. I had about 25 pounds between all the sweet and sour cherries, and today have made 3 pints of sour-cherry jam, a double batch of boozy sour cherries and now, this sweet cherry-plum jam courtesy of, wait for it, the Food in Jars cookbook that I seem to be having a real Julie and Julia moment with. All that remains are a quart of sweet cherries and probably a similar amount of their sour pals. I'm thinking about making a pie with them...