I had been using them together for a bit, although would never progress far enough to start using upgrade plus. However, after using an armor set for an extended period I realized I wasn't getting benefits from it. So did some experiments and found that (for defense atleast) the two mods collide, stopping yours from applying defense benefits.
I'm not sure if it would also break other functionality for armor upgrading also. Not sure if theres anything you two can work out. But just letting you know.