Add the stick — flex mode handles mismatched RAM.

Yes, it’ll work. Flex mode is designed for exactly this: one channel has the full soldered 8GB plus the SODIMM’s 8GB, the other channel gets just the soldered 8GB. The system runs dual-channel for the first 16GB and single-channel for the remaining soldered portion. No stability issues.

The real concern is not matching specs — it’s that the SODIMM is compatible. Buy a stick with the same DDR generation, speed, and voltage as the soldered RAM. Usually that’s DDR4 3200 or DDR5 4800. Check your Latitude’s manual or the factory RAM spec sticker. If you get that right, flex mode does the rest.

Don’t overthink dual-channel performance. For most people, the difference between flex and full dual-channel is under 5%. You lose a tiny bit of speed when the system accesses that last chunk, but you’re doubling your total memory. That’s a massive win for multitasking.

Just make sure you power down fully, unplug, and drain residual charge before opening the laptop.