I'm not much of an expert, but I read "The Animator's Survival Kit" by Richard Williams, and he says the arms are at their widest on the *down* position. That isn't exactly "one frame after the contact frame" like I said, but it could be, depending on how much frames you use for a walkcycle.

Looking at your frames, your hands seem to be at the widest on the contact position (the frame where the heel of the leading foot touches the ground).

Looking at your frames, your hands seem to be at the widest on the contact position (the frame where the heel of the leading foot touches the ground).