M21 4 Spring clutch rod length?

[watts]

I have given up on my 6 spring.

I have fitted a 4 spring but I think the rod is too short.

Has anyone done this and what length rod do they use.

I thought I might cut it and insert a few ballbearings in tube to make right length.

Also it has a lot of plates and very stiff springs should change this?

Thanks

Matthew