That is a very interesting approach Dave.Henro
My experience is to leave the belt off one pulley and get the spring in place.
I then rotate the mower spindles and lever the displaced belt into place using a flat bar between the pulley and the belt. As things rotate, the flat bar moves past the pulley and you are left with the spring and belt all in place
It seems easier than dealing with the spring with the belt around all pulleys.
Dave
Thanks for that idea!