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Has anyone tried substituting dried buttermilk solids for the powdered
milk? (For those not casein/lactose intolerant)
 
Buttermilk is naturally tart, which "balances" the base pH of the rice
flour...so it replaces the vinegar.
 
I don't have an exact measurement for you...something like 2 tablespoons,
figuring that 1 tbls = the amount to reconstitute one fluid cup.
 
I was able to find buttermilk solids both at my local health food store &
also available commercially in a local supermarket, in the aisle
dedicated to baking supplies.
Bec