One difficulty here is that "slipstreaming" bikers frequently choose large vehicles to "hook up to." Some truckers have NO sense of humor about this. The "potential" is sometimes "dead."

A group of bikers traveling together can get some significant drag reduction, particularly if they ride "in-line," or "in-echelon" like the geese do. It is necessary to adjust the spacing between riders pretty precisely for best effect, but you do "feel the sweet spot" if you get close to it. Contrary to the "obvious," even the guy in front gets a little help, although less than those following. It relates largely to the playoff between effective L/D (length to depth ratio) traded off against "interference drag."

For the "classic" analysis, look up the "Busman Biplane" ca. 1943 or so. Walter Beech used the concept in the "Staggerwing" Model 17 biplane, where the upper wing effectively "slipstreams" the lower (more forward) wing as airspeed approaches maximum - to get a few more knots out of a relatively puny engine.

Yeah, I know you guys were makin' jokes, and it's more than you wanted to know, but...

John