($S_{StreamLength}$ duplicated from Tapping Stamina)
Documentation on the logic behind Strain-based Stream Length is located at this section in Tapping Stamina:
Strain-based Stream Length $(S_{StreamLength})$
Here are the slightly modified equations used in flow aim:
x = MS difference between the current circle and the last
$$ c_{ircWorth}\left(x\right)=c_{lamp}\left(\ \frac{\left(t_{oMS}\left(160\right)\right)}x,0,1\right) $$
$$ c_{ircPenalty}(x) = 1-c_{lamp}\left(\ \frac{\left(t_{oMS}\left(180\right)\cdot2\right)}x,0,1\right) $$
$$ c_{totalWorth}\left(x\right)=c_{ircWorth}\left(x\right)-c_{ircWorth}\left(x\right)\cdot c_{ircPenalty}\left(x\right) $$
$$ c_{ircWeightage}=c_{ircWorth}(c_{irc})\ - c_{ircWorth}(c_{irc})\cdot\left(c_{ircPenalty}(c_{irc})\right) $$
Where $c_{irc}$ is the ms time of the current circle compared to the previous.