Long headshell required

If the arm base is "so large" making it difficult to locate closer to platter, then the P2S distance will be longer not shorter.

You are right, @solypsa. Good catch! But my point is the same - increasing overhang won't offset a misaligned P2S distance.

Thanks for all of your suggestions.  Since I'm not prepared to cut out the plinth, it's the best way to improve the P2S distance.  It wont be perfect but it will be close. 

Does anyone know of a long SME headshell?

Changing the overhang will not in any way affect P2S distance. I don't think the headshell you seek exists.

Something like this might works:

https://www.audioadvisor.com/prodinfo.asp?number=VPHW