I'm sure there's a limit, but it's not really that big an effect as you'd think. The fairing is lifted almost entirely by the first stage, and as SpaceX increased confidence in the landings they were able to reduce to fuel margins, leaving move for a heavier fairing. The aerodynamic effects are secondary to the added weight, and are only a really a bother for a few seconds at max q. In fact, the larger volume to surface area makes designing for max q easier in some respects, such as audio energy.