RE: What windspeed grounds you?
Here's the method I use, it should be adaptable to everyone, especially when the wind is right down the center of the runway because "Two Mistakes High" is relative to your skill as a pilot and your plane:
1. Take off and fly into the wind about two mistakes high.
2. Pull up and do a hammerhead at the upwind end of the runway with the vertical leg about 75' high, keeping the wings perpendicular to the wind.
3. If the aircraft is blown more than halfway back down the runway before you have to pull out on the down leg, it's a little dicey up there and I'll consider cutting the flight short. If the plane gets blown more than 3/4's the length of the runway, it's time to land.
Exeter,
Radio Shack has LED's and micro-switches much cheaper than any LHS or on-line RC store than I've seen...
Ed