Rega RB 600/Grado Ref:do i need a spacer?

I just ordered Grado Reference MM cartridge for Michell Gyro SE/Rega RB 600.I am using a 2mm spacer right now for Shelter 501 mkII.Do i need it for Grado also? Thanks a lot.
I use a Rega supplied 2mm shim on my Rega RB 1000 mounted on a Gyrodec. The cartridge is a Lyra Skala. IMHO try the Grado with and without the spacer and go for whatever sounds best to your ears. Rega believes that VTA is something you should not be too concerned about...and yet markets these tweaks !!
Best of luck