Hi there,
For any hardware setup, you have to check the specification and the compatibility of the MOBO with other devices. For RAM setup, all the sticks will need to run at the same voltage, speed and timings. If any one of the statics are different to each other in settings, then the RAM channel configuration shows as incompatible or it will unrecognized by the MOBO.
In your case, you might need to up the RAM voltage a bit to compensate for new setup.
Good Luck.