With first runnings and two sparges (all equal volumes), my numbers work out 50%, 33%, 16%. If I was doing this, I'd split the sparge water into three batches. First runnings and first sparge in the IPA.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk