SPU cartridges and washers

I am using an SPU Synergy G II with a Sorane SA 1.2 tonearm and wanted to get advice please about using a washer between the SPU and the tonearm socket. I bought the SPU new from an Ortofon dealer and apart from a sticker on the box saying SPU Synergy G II there is no specific information about how to use this cartridge. Even the range for VTF until recently said 2.5 - 3.5g and is now changed to 3.0 - 4.0g in Ortofon's literature ...?
As with all such questions, try each way and see. Whatever sounds best, is best.

If you are worried about VTF, why? There is overlap between 3.0 and 3.5. So use whatever sounds best that falls between 3.0 and 3.5 that's always how VTF is set anyway- first within range, then from there by ear.