there are wind tunnel tests that show the most aerodynamic rim/tyre combo is when a rim is 5% wider than a tyre. practically though, such setup makes the rim vulnerable to scratches from the curbs etc.
to answer the original question - i've ran a719 rims on my hack bike for a decade, always with a 25mm tyre, never had any problem. i also have 25mm tyres on 21c internal rims at around 80psi, also no problem.