Grab some cashews and run your experiments.
Learn what's enough to remove the testa without harming the product.
Also, to what extent are you removing the testa?
I would approach this problem by first estimating the force it would require to bend one of those springs by approximately the width of a cashew. Then assume how many would be in contact with a cashew at a time (3 maybe?). Now that you have an estimated force you might be able to set some relationship between that and how much force would be applied to a nut sliding on a surface just prior to damage.