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I was able to upgrade, both RAM slots were swappable (not soldered) and side by side (not overlapping like the older 2500u model) under a silver heat shield with gold colored thermal tape. Mine came with 2x 4gb Samsung modules and had no problem taking 2x8gb Corsair's Vengeance 2400mhz. Total time was about 15 minutes to change.
Due to the disassembly required it is considered to be inaccessible, however there is 1 free RAM slot on the board which you could add another 8GB and make 16GB total.
This model does not have upgradeable RAM.