we both need wind to move. If we have less than 8 knots of wind it doesn't make any difference what sail we have up or how light is, we just can't move fast enough to make it worth while. When Steve and I were talking about 3/4 vs. 1.5 oz we both knew that if the wind was so light we needed a 3/4 oz sail to keep it up we would without question start the engine.
We use ours in 8 to about 15 true. It wouldn't make sense to try to move any distance with only 6 or 7 knots of wind. We'd both die of boredom at 3 knots boat speed.