I just don't see how a plinth with effect the 'sound'. Caveats, as long as all the comparators meet the above criteria, i.e correct, dimensions and sturdy enough for the job.
I'll go further, I don't think a top plate effects the 'sound', neither does a sub chassis. They have to have the correct dimensions and be true, if that's the case, then their all the same, there is no 'sound' difference.
Whilst were on the subject, as long as the wire is the correct specification for the job of conveying the signal to the phono stage, that doesn't affect the 'sound' either.
How you bolt it all together, different entirely!
Great post - I've got my carton of popcorn at the ready!