The chipset in the (QC version of the) W510 is actually exactly the same as in the X201 and T410s: Ibex Peak.
But CPUs we are looking at *are* actually different - scale-down could mean an exposure of a previously unaccounted design issue which actually prevented 32nm CPU 'upgrade' to work reliably with >8G of RAM... And AFAIR nobody ever reported to break official memory limits within an entire family, I`ll be happy to know that this is not true.
Just to add .02c - DDR3 interposers from tek/futureplus are appearing on ebay relatively frequently and for moderate price, so if someone has will to spend some effort on this task, the analyzer coupled with interposer could provide great help, with regard to unstable behavior with a single 8G DIMM.