well everyone can complain about the fall off but all the drivers had to deal with it... just some might have more exp for what changes to make between the first and second run.
and yes foam doest degrade lap times... but that is why the US guys can win foam at the IIC but we get killed when we toss rubbers on.
but there is a major down side to foam.. one wrong tap from another car or wall the pair is trashed and your run is toast.