It is not possible to give a breakdown of the different sectors because it will depend upon the starting technique of each individual and how they change. And, of course, those already having good technique (such as demonstrated by Cheung's left leg) wouldn't be able to achieve such a large improvement. That having been said there would be an "average" improvement looking at large numbers of individuals and current "typical" pedaling technique seen in most and if I were to do that I would anticipate that there would be, on average, 3% improvement seen on the downstroke (between 45º and 135º), 12% improvement seen on the backstroke (between 135º and 225º), 10% on the upstroke (between 225º and 315º - what happens if you just get rid of the negative forces), and 15% seen at the top (between 315º and 45º) adding up to 40% improvement overall. If we were to look at someone currently at and FTP of 250 watts 40% improvement gets them to 350 watts, a 100 watt improvement. 7.5 watts would come on the downstroke, 30 watts on the backstroke, 25 watts on the upstroke, and 37.5 watts over the top. Note, the biggest improvements come from improving the weaknesses, not trying to improve what is already strong.