A question about a recipe: Just Peachy Pie

When I tested the recipe I used quick-cooking tapioca and was unable to source sour cherries; it was all delicious!

Substituting one dried fruit for another in a "wet" recipe is always fine.

I'm not a fan of thickening my pie insides with such powerful thickeners as tapioca or cornstarch. I much prefer the {very old fashioned} mainstay: flour. I find that whole grain flours thicken better and you need less than you would an all purpose, pastry or cake flour.

The way I try to ensure that my pies do not get too runny is twofold:
I bake the pie 24 hours before I am going to slice it, but I keep it at room temperature the whole time.

I do not pre-macerate my fruit. I have all ingredients ready to go and pop pie in the oven as soon as pie is assembled. If I have to make more than one pie at a time I make the extra pies wait in the freezer and them I put them all in the oven at once. I always start my pies in a hot oven to gain color, and then I turn down the oven for the remainder of its baking time.

agreement with drbabs-- blueberries would be great too (use 2 tsp of lemon juice), and yes, you may substitute an equal amount of cornstarch or flour for the quick-cooking tapioca. i recommend quick-cooking tapioca only because it *consistently* delivers non-runny pies. cornstarch used to be my go-to, until a recent string of river-like blueberry and sour cherry pies. i still always use flour to thicken my apple pie. it all depends!

let me know how it turns out!

Yes, I think blueberries would work just fine. You could substitute cornstarch or flour, but tapioca is a really nice thickener so it would be worth seeking it out. (I get Bob's Red Mill tapioca flour in my regular grocery store.)