THE Daihatsu Sirion backs up its distinctive, quirky appearance with clear evidence of design competence. It scores well for safety - dual airbags are standard - and caters for passengers and their luggage very capably. The diminutive three-cylinder engine also performs strongly in its intended environment, helped largely by the fact the Sirion is a real featherweight. This factor influences the fuel economy, making the Sirion an eminently sensible town car. It also contributes to the Daihatsu's tendency to feel somewhat flimsy on the road.