Once all of the hydrological and hydraulic properties of the model have been set, the model needs to be run in a Time Simulation.
Here it can be seen that the additional pipe is operating at 86% of the maximum fraction filled.
The existing bulk stormwater line (link 3 (and 4 by extension)) is operating at 76% of the maximum capacity, which can be deemeed to be acceptable, and allows for the additional pipe to be run only half the length to the outfall.
This process can be iterated depending on the additional capacity margin desired.
Thank you for following the tutorial!