Thanks for that recommendation. I've updated my code. However, the call to remapper->Apply(eeh) still is failing (returning false). Maybe because the ElementPropertiesSetterPtr only has a new DgnFont specified? Should it somehow be "initialized" from a ElementPropertiesGetter ?
I think there is a problem with ElementPropertiesSetterPtr::SetFont(). If I set other properties (like color), the text's color gets changed, but the font does not (at least the Apply() function returns true).