Yeah. Best experiment I could think of would be a coast-down test, pedal it up to a certain speed, stop pedalling and see what the speed each second thereafter. A phone app w/ GPS might possibly be accurate enough to do this and log it. Do it in both directions and you could potentially account for gradient and wind, assuming the latter remains fairly constant. A phone app connected to a sensor counting a magnet on the wheel would be more accurate tho.
(Since the jet is yet to be attached).
But yeah, super-hard to work out a theoretical calc for the pictured bicycle with you on it. I guess that racing bicycles are relatively well-modelled and thus reasonably representative figures are known, but this thing is a lot different from one of those