IMHO, judging temperature by "hand count" can never be more than an approximation. You could be off by 30 degrees, and that will make a difference in the results. You can find a decent mountable thermometer on the web for $20 or so. Buy one, and mount it so the probe is near grill level on the side where you place the food when cooking indirect. Then you'll always know, not guess, the temperature.
If you don't like the food, have more wine