Jelco sa 750e

Ahh so I need to measure the hole as well

makes sense 

It’s 1.25 in

So 1.25 inch = 31.7 mm

Basically you could expand your mounting hole towards the platter by only 0.39 inch to mount another tonearm with 230mm (9.05 inch) Pivot to Spindle distance like Fidelity-Research FR-64fx. The top plate of the FR tonearm base will cover 53mm (2.08 inch) diameter above your plinth anyway.

Look at FR-64fx in my system (in the middle of the picture gallery).

Looks really solid, I was about to make a trade for a sp10 that had a fidelity research fx64 s on it but he backed out.

I read that if the vtf was hard to turn it would need to be cleaned and regreased

Did you have your cleaned and regressed?

the plinth is corian several layers I’ll have to look into what to drill it with

thanks

I read that if the vtf was hard to turn it would need to be cleaned and regreased

Did you have your cleaned and regressed?

I did, but only on my 66fx and only because the side panel fell off on arrival.
Look at the VTF spring of my 66fx with new grease.

My NOS samples of the 64fx are all fine, two of them. I also have 64fx PRO and it’s also fine. As you might know the fx series was made in the '80s and overall quality of some parts are better than old 64s from the early '70s.

The armlift and arm base are better on FX, dynamic tracking force is always in better condition that on 64s.
So the problem you are talking about is a common problem for 64s , but not for FX series.