I make this in large batches and use 1:1 in everything.
Err to the side of a bit more rice flour than starch.
Andrea tells me that it rolls out well for pastry. I have tried it in Chocolate Chip Cookies. (Just a note that when using this flour in the Chocolate Chip Cookie recipe the baking time should be increased to about 18 minutes for the first sheet and about 15 minutes for the additional sheets. You will have to play around with the times depending on whether you want a chewy cookie or a crunchy one.) She has had problems with yeast bread.