10 kt is my lower limit for a good drift fish on the flats, but somewhere around 18 kt is where the drift loses its charm - the upwind paddle becomes taxing, control of the boat is more difficult, and everything happens so quickly, the drifts may not be worth the paddles to set them up.
Neumie and I fished East flat on Mustang Is at this upper limit, and really was the upper limit of where you'd want to be out, and with that we were both in wind-slippery boats. viewtopic.php?f=8&t=249702
The day before, we had called it when the SSW wind shifted to W and 18 kt, and we had just one mile to paddle into the wind to get home - it was enough. But I've also out been trying to paddle due W on a similar strength SE wind when it became difficult to make the small upwind reach to get the last 20 or so yards out of the ICW - if you're in a boat that sits high, this could put you in a turtle situation.
Kinda interesting, going back to experience when my dad first retired in the '90s, drifting LLM East of 3 Islands and Oilfield flats, and Green Is, the same limits fit. Sitting on an expansive flat with no wind is no fun (need a new plan, like find a cut or slope with a tide current to fish into). Above 18 knots, even running a power boat to get there and back is rough. I know Tobin posted his recent success on LLM with greater wind, and while it can work, it's really hard on you even in a power boat. Tobin's success was focusing on structure where the bait couldn't get out of the wind.