torsion springs have a rod going through them making them a bit safer
than an un-cabled extension spring correct?

Perhaps safer in terms of becoming a projectile, but when a single torsion
spring configuration fails the door is fully heavy, versus a double spring
configuration (extension or torsion) where one of the spring pair remains
intact so that the door is still a hazard but half as heavy.

http://www.truetex.com/garage.htm