My guess, and it is little more than a guess, is that a windshield adds 12-13% range at 75 mph. 12% of 58 is about 7, so Bill's test might be evidence of a 51 mile range at 75 mph without a windshield (and you've got a pretty significant shield -- less than "touring" but more than "sport"). I mention this only because range figures for the current electric bikes are for the naked stock versions.
