i compare 4 dimm and 2 dimm, conclusion, i think no need for 4 dimm
here my test result, all test vdimm 2v, memory apacer 2800c17 4X4gb
2dimm bench spi
2dimm bench xtu
4dimm bench spi
4dimm bench xtu
2dimm if you can trust your hand, we no need 4 dimm, just push to the limit :D