The term "more king size" implies an increase in the size of an object, specifically in comparison to something that already has large dimensions. The antonyms to this phrase, thus, would be words that imply either a decrease in size, or a variation in dimensions. Some antonyms for "more king size" could be small, tiny, miniature, diminutive, or compact. These words describe objects that are smaller in size, which is the opposite of the larger, more expansive dimensions implied by "more king size." Choosing the right antonym will depend on the context in which the phrase is used, and on the writer's intent in emphasizing size or variation.