When subbing for arrowroot what’s the blend or tapioca and/or potato starch?

I'm trying to figure out how to replace the potato starch in this recipe since my son can't have it. I usually replace it with arrowroot: 2 tsp arrowroot to every 1 tbsp potato starch, but the recipe already calls for arrowroot. Has anyone successfully replaced it with tapioca flour? And if so what ratio did you use? I find tapioca flour can makes things gooey, and I don't want that. Maybe I should just add more arrowroot, but I don’t want to dry it out either? Since this is a bulk recipe, I'm afraid of wasting ingredients, so I thought I'd ask first! Thanks in advance!

My son has a millet intolerance could I just use brown rice flour to sub?

Does it make a difference if I don't mill the grains? Is it the same amount of each ingredient bought from the store? I already have most of this anyway.

This is an excellent diy blend, which allows us to use all organic ingredients and to mill the grains ourselves for maximum nutrition. We have used it successfully in several recipes on this app as well as an old family favorite that originally called for AP flour. Highly recommend!!

Just following up on my original question about milling the grains fresh for this recipe. We used 135g per cup of grain, which comes out to: 202g Brown Rice 405g Sorghum 405g Millet Then measure the other ingredients by volume as listed, since those are not milled. Our process: In our large stock pot (so we have plenty of room for thorough mixing without spilling over onto the counter), measure out the last 3 ingredients by volume since they can't be milled. Mix well with a whisk. Then in a separate mixing bowl we WEIGH out the grains one by one and then mill them right into our stock pot which already holds the starches and xanthan. Then we can stir everything together really well before freezing for later use. We have used this blend in several of the recipes, including hamburger buns, cinnamon rolls, chocolate cake, and also an old family favorite recipe for pumpkin muffins, subbing this blend for the AP flour it called for. Everything has turned out beautifully!! I am so, so grateful for this much more nutritious GF option. Looking forward to using it in other applications too! Thank you, Jen💕💕💕

Does this flour blend work with any other recipes or just the bread machine?

To make this mix fresh milled, how do you know how much of each grain to mill, since fresh milled flours don't measure out cup for cup the same way store bought flours do? And I also would like to avoid milling more than I need due to guesswork. Do you just measure out 135g per cup of each grain and then mill it? Hope my question makes sense!