These curves show the upper limits on the size of delays from second-order ISM effects extrapolated up to higher frequencies. The dark grey area is for PSR B0809+74, which had the largest RMS residuals in our timing fits; the light grey area is for PSR B1919+21, which had the smallest RMS residuals. They are scaled with ν^-3 and ν^-4 which are the lower and upper bounds for scaling of the second-order ISM effects.