In support of, and in addition to Mr. heedm's comments;
Perhaps this thread is looking at two separate contributors to lead/lag.
1/ In forward flight, when the tip path plane is low at the front and high at the back, the Cyclical Coriolis Effect (Hookes Joint Effect) will cause the tips to lead when the blades are pointed forward and aft. This is due to the shorter moment arm from the mast to the center of the blade's mass.
2/ The lag on the retreating blade, which was mentioned by Mr. Zuckerman, may be due to the fact that the greatest portion of the profile drag on the retreating blade is out near the tip. On the advancing blade, the profile drag will be more evenly distributed along the span of the blade. The length of the moment arm to the center of the drag on the retreating blade will be greater than the length of the moment arm to the center of drag on the advancing side.
1 & 2 revisited/. Any lead in the forward and the aft pointing blades may require that Mr. Zuckerman's "peace sign" be rotated by 1 or 2 degrees. This rotation may result in a picture that appears to show the retreating blade as having lag.
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An additional comment could be made regarding Mr. Zuckerman's "peace sign", but this is probable not the time or the place.
