Swapping Platters on Thorens 124

I have been told (by Art Dudley) it is the sub-platter on the Mk.1 that is ferrous, not the top platter. True or false?

Yes, that is the case. I have an aluminum top platter which is a great upgrade but still use the iron bottom platter. I've just purchased a Woodsong Audio thingy that replaces the pop up 45 mechanism so any mat will work and I bought an Achromat to hopefully raise everything high enough so the Decca will work. Fingers crossed. 

Thanks @dhcod. I too use London's, and am myself interested in getting TD-124. Keep us appraised, ay?

I have a MKI with the Woodsong hub replacement and a Tenuto mat. I have no problems with my Decca’s or SPU’s. That said I didn’t have a problem before I had the thick Tenuto mat either. I know these issues must be based on some type of genuine historical mismatches, but I’ve never had a problem. Just make sure you measure VTF from on top of the platter. I do notice VTF increases on top of the platter vs outside of it, but this hasn’t been detrimental to my ears. 

That's very interesting! Thanks for the info. Looking forward to giving it a try.