removing the headlining for the sake of 1.5kg is a bit daft. it seems ok til you get constantly dripped on by condensation.
Ah but it is 1.5kg that is high up and will also reduce your centre of gravity, (only by a small amount I know) plus extra weight for the bits of trim holding the headlining up which I didn't count in the headlining weight.
Haven't had the condensation problem, even when its been tipping down all day and the windows are all steamed up.
Perhaps there's too much hot air in your car
Paul