There were rumors about 16GB variants of the RTX 2070/2080 but these models never hit the market. The 16GB mod was performed by replacing the memory modules plus changing resistors into a different binary code. The BIOS on the RTX 2070 card supports 16GB and the card is recognized properly by GPU-Z.
VIK-on managed to run some benchmarks but overall the mod isn't successful as the card has stability problems.
VIK-on was able to run the full 3DMark TimeSpy test. The card scored 6176 points in TimeSpy Graphics, which is well under the average score for RTX 2070 of 9107 points. In the end, it appears that the hardware modification was technically successful (booting into Windows is already a great achievement), but the card was not stable enough to consider the whole endeavor a complete success.