How to refit an Aluminimum Window Sash

[echnidna]

I need to refit a vertical sliding aluminium window sash.
Thats easy enough, I worked out how to do that.

How do I fit the spiral suspension unit.
Should there be one on each side of the sash?

[Tools]

There should be a spiral balance on each side of the sash.

Here are the fitting instructions.

http://www.whitco.com.au/infoCentreDocuments/1282M%20SpirTubeUnit%20fit.pdf

Tools

[echnidna]

Well the instructions sound easy enough.
Pity the windows themselves haven't read the instructions.
Fiddly pain in the neck job.