OK, Second test completed this morning. No results yet - will try to get online today.
Managed to get a full run of speeds for:
1. Specialised Decibel (non aero)
2. Limar Chrono 05 (aero)
3. Giro Advantage 2 (aero)
4. Specialised Decibel (non aero)
Unfortunately there was a bit more wind at the end of the test, will see if that affects the data. Dead calm at the start. Runs 1 and 4 should be very close together on the graph. If not ... maybe indoor velodrome time ;) . Also used spoked training wheels instead of disc/H3 to try to prevent any wind on that gear lowering CdA.
Subjectively, at speeds over 40 the two aero helmets felt significantly easier to maintain speed than the non aero lid. Max speed was about 50kmh.
All the other parts of the test were OK - constant Ergomo offset at beginning and end, consistent use of the selected speeds, consistent riding position (head up looking 15 m in front of the bike, still shoulders held in same position, knees just brushing the top tube all the time, same seat position, stayed away from drafting other track riders).