Spindle-To-Pivot Distance

some headshell/cartridge mounting flexibility might allow for adjustments of a mm or two.....but it’s not a good way to jerry rig things as you would be forever fighting it.

in addition to distortion, miss-mounting the arm could cause records to skip, and harm the grooves. it’s basically not an option. you would be better off listening to digital.

maybe you could approach this differently; and ask for help with arm board ideas to solve your geometry/spindle to pivot distance problem, assuming you are stuck with that particular tt, plinth and arm. tell us about the tt and arm.

possibly does it use an arm board which could be made larger/longer?.........over the edge of the plinth? can an inset into the arm board possibly allow for a different mounting point for the arm? i’m just trying to help you visualize a way to mount the arm at the correct distance.

or.....let's say you have a wood arm board now. and making a longer wood arm board might not be stable enough. but if you had one that hung over the plinth made from stainless steel, then it would likely still be stable. not sure that is relevant, but getting a hunk of stainless drilled properly might be cost effective.

You asked whether I have experienced this. The answer is yes. About 25 years ago I once fitted a Rega arm to a Project turntable in place of the Project arm. The effective lengths of the arms were different by a similar margin.
I didn't know much about tonearm geometry then and I wanted to see if it would be an improvement. It wasn't. The result was exactly as I described - mistracking and distortion.

So I can tell you from both a theoretical perspective and from experience that it is a bad idea.

If someone actually did this and heard it sound that bad then there you go.

Sounds like you could do it right and only have to put up with it looking bad. If that is the case looking bad is better than sounding bad.

Make a mounting plate that will hang over the edge of the plinth. Wood will do fine! Or use acrylic! A rectangular piece with a mounting hole.