Keep in mind that sometimes a lower setting will actually move more air farther up over your head due to the tunnel effect of the outer shield working with the inner shield. If you have the shield up high there is less of a tunnel between the two shields. A taller shield set low will be better than a shorter shield set high.
Also an angle too far forward will give less lift and more disturbed air. That is why Madstad suggests (I think it was) 60 deg.