There is a phenominon known as 'vapour lock' as well.
Where, if a pump is asked to suck fuel a long way, it can lower the pressure at the pump inlet enough to boil the fuel (very local boiling I'm talking about, around the impella blades of the pump), and essentially it casues the pump to try to pump fuel vapours, which is not a good idea.
This phenominon is worse if the fuel is hot already (from either too big a pump, or fuel lines running close to hot things).
so yeah better to get as much positive pressure as you can at the inlet of the pump, which can be done by mounting it closer to the tank, or as suggested lower to the tank.