bob,
get a bench vice. drill & tap vertical holes in the top of the clamping surfaces (and install bolts) or use safety-wire around each end of the vice.
run the jaws together enough to hook the spring ends, to either the bolts or the safety-wire loops.
unscrew the vice using the handle.
when the spring is extended enough, install a nickle between each gap on the spring.
screw the jaws back toward each other, & removed the spring from the vice.
set the chair, to a point where the spring would be at it's lowest tension. slip the spring onto the posts/hooks on the chair.
remove the nickles.
it worked for me.
chuck
June 2008