If you run a calculation and find that your Flow lines are too thin, then you will want to check the following:
1) Drawing and Flow Planner (settings) units. It is important that your Drawing Scale Units are Inches if your Flow Planner settings are in Inches or that both are in Millimeters depending on your situation.
2) Path Trip Frequencies should be checked in the Path Tab. Remember that the thickness of a flow path is based on the number of trips (more trips equal thicker paths). Multiple trips are caused by large Product quantities divided by small parts per delivery (i.e. Parts Per Container multiplied by Container Per trip). If you have fractional (i.e. 0.05) Trips per time then you will have very thin lines.
3) Finally, make sure that the Path Thickness factor is properly set in the Paths tab.