Excluding the gift shop (but including the lockers), Mummy/Kongfrontation makes up barely .02 acres larger than Reign of Kong's size.
But including the showbuilding in whole mass, then yes; it's larger than Reign of Kong by nearly .25 acres.
Reign of Kong, if it wasn't in a period of time crowded by screen inflation by both Universal & Disney; would be highly praised for the blending of the two. And Reign of Kong is still the most practical attraction made by Universal, since Forbidden Journey (as much as I LOATHE saying that). Not to mention it quite a large amount of practical elements, and has mainly 3 screen based portions (bat's, which are practical right before), the carnictis (which, HAVE practical versions in the queue), and the 360 scene (which is updated from the Hollywood counterpart to match the ape from the finale).
Outside of those three, there are virtually no screens elsewhere. Not to mention the moving drivers in the actual vehicle, Kong himself, and the tribe; there are a lot of practical elements.