Lapels speak generally to formality more than to body weight or type. Peak lapels are the most formal lapels (you see them on dinner jackets for both white and black tie for example). So to answer, yes they are perfectly acceptable and in fact, if the coat is a double breasted, it would be required (imo).
Thanks for the pointer. I guess my confusion comes from having noticed quite a few younger professionals (like myself) sporting peak lapeled single-breasted suits lately. Often these are somewhat narrower than traditional peak lapels, but nowhere near as narrow as the fairly recent trend of super-slim notch lapels. They definitely don't look "formal" they way they are worn (often paired with very loud shirts, cheap ties, and even student backpacks). I was aware that tuxedos should be peak or shawl-lapeled, mine (Indochino 3-piece) has a shawl lapel. But I was shopping for a new navy M2M suit and was considering getting it with peaked lapel.