No toeclips? You’re wasting a whole bunch of efficiency there. By using your upstroke you can gain much more power.

Power, maybe. Efficiency, no. You use energy when pulling the pedal up with your leg, energy you wouldn't otherwise use if you were just coasting with it on the up swing. Not knowing anything about anatomy and muscular dynamics, but it might actually be less efficient since the muscles in the human leg aren't meant to pull up loads other than its own weight under any evolutionary circumstances.

Anyway I use the heavy military bicycles to offset my otherwise sedentary lifestyle, so maximizing efficiency would mean I wouldn't get the same exercise as before. In fact I don't understand some cyclists with their over thousand euro super bikes with gazillion gears and carbon fiber frames. Surely if you want to get fit and be 'sporty' you should pick the heaviest bicycle you can possible peddle with? And the speeds they reach begin to be quite dangerous, at least to other cyclists. And if they want efficiency they should stick with speeds under 25km/h since above that you actually waste most of your pedaling effort into forcing air out of your way.