The phrase "more plain-dealing" suggests honesty and transparency. So, the antonyms would be words that indicate deceit, concealment, or manipulation. Possible antonyms could include words like misleading, dishonest, disingenuous, fraudulent, insincere, or secretive. Using these words in place of "more plain-dealing" would change the meaning of the sentence entirely, conveying a sense of dishonesty or lack of transparency. It is important to be aware of antonyms for words, as they can completely alter the intended message and impact the credibility of the speaker or writer.