OK, if ya fill in your AC environment and put 'em in your vehicle, what's the temp diff? You're in Tenn with a heat wave. So let's say the AC temp is 72° F and outside ambient temp is 90° (you wish!). That will cause an expansion of the juice in the FULL cart/carto = leaks!
Now, as to temp and juice fragility... A lotta folk insist that heat is THE WAY to steep.
So, under fill and leave 'em in the vehicle... Two birds with one stone!