I noticed that the springs used in this guide are different product number than SW-T600 use.
SWT-600 used product 22401-MCT-000 and those lenght are 31,80mm. I streched these to 33,00mm. Little less than guide recommend, 1.2mm. Older Silverwing use little shorter springs. Anyway, regardless of model, stretch 1.2-1.6mm.
Interesting would be if you can use SWT600 spring on your older Silverwing model. Newer model use 0,6mm longer than older model. Then you dont need to do anything. Just, bought newer , SWT600, clutch springs.
About clutch squeal. I think that this mod help for this because clutch pads take a full contact faster. My SWT600 squeals when I bought it but I sanding clutch pads and clutch bell. It never come out after that. Even with this mod.