[PvK]

There is essentially never any problem with this in my Proportions mod, for example, because planets can hold a lot more than transports can easily bring to them, both in population (because you can usually only get about 1-2M at most per transport), and other cargo (because I turned up the planet capacities a whole lot - I didn't like running out of room on planets, for realism reasons).

Planet capcities are controlled in PlanetSize.txt.
Population size is in Settings.txt.

PvK

Edit:
You probably want to make a mod to do this, rather than editing your main files, unless you don't want to play with other players at all. Otherwise, you would get Version conflicts and want to apply the Unmod to reset your data files to default.