Dicks Racing has done a few members bikes in the 01-02 era with reported good results.
As far as you wanting a softer spring, go to the
2001-2002 Parts Manual and look at the rear shock.
Your 01 470 FXe came with a PDS7-260 76-95 N/mm
The FX's and FC's (Desert and Motocross versions) came with the stiffest springs.
You could drop down to the softer 2002 enduro spring a PDS6-260 which is softer @ only 71-90 Newton meters.
The 260 number is the length (in MM) of the spring.
PDS is Progressive Dampening System which refers more to the shock but the springs are progressive too hence 70-90.
There are eight springs listed and 4 are optional.
Study the different springs. The White power springs are commonly referred to by there first four characters, PDS3, PDS4 etc.
Something to ponder, only the supermoto versions came with a straight wound 250mm 84 N/mm spring which does not have the PDS designation.
I bet you could find a complete used shock with the spring you want and have a spare for parts. Have the better of the two rebuilt and perhaps revalved if they have the specs and experiment with different springs.
The same shocks were used on KTM,s of that era too, although the internal valving may be different the springs would be the same (a PDS3 is a PDS3).