Right - the bar stiffens the existing torsion beam, so it's mounted directly to it and not tied in to the chassis.
is there no linkage that connect the swaybar to body/chasis? whether the swaybar only mount on the torsion beam suspension?
I put a similar 19mm rear bar on a late 1970's MK1 VW Rabbit/Golf with a similar torsion beam like the Mirage, and it made a very big difference in reduced body roll. The car felt like a go kart. But the ride suffered a bit over uneven bumps (no difference over bumps that are hit by both rear wheels at the same time).
View my fuel log 2014 Mirage base ES 1.2 manual: 54.0 mpg (US) ... 23.0 km/L ... 4.4 L/100 km ... 64.9 mpg (Imp)