The spoiler lip on the boot lid, painted in the vehicle body colour, reduces lift at the rear axle and thereby increases driving stability at high speeds. (ausmotive.com)
But to be honest, the standard system is hardly bad, and is perfectly capable even at higher speeds with the top down. (autoexpress.co.uk)
The most common cause of a rollover collision is travelling at high speeds while driving on a curve. (citrusinjuryattorney.com)