Pathological example of a intersample peak, 11dB

Probably not a big problem for the test you are doing, but your input sample is a bit weird -- not even vaguely symmetrical. Here's a way to generate a clean input sample:

sox -r 44100 -n InterSamplePeak2.wav synth 220501s 0 25 sin 22050 repeat 1 fade h 5 10 5