I did some tests on flap reflex angles vs IAS and weight. During a test with a Swiss-Air pilot aboard at 9500' dalt, going from 8 deg reflex to 6 deg caused a 3 mph increase; from 6 to 4 dropped the 3 mph; 4 to 2 dropped 3-4 mph more. I found that by having an RV level in the cockpit set to the chord-line at about 40% span, and setting it to about 0-1 deg nose-up by adjusting reflex gives about the best speed under most load and speed conditions.