Sand: I agree that it's difficult to be aero at 35+, but if you can, your gains will be fairly substantial.
Oh, I agree. That particular stretch of road, though, has its issues. The curves on the downhill really are too tight to stay on the aerobars. Maybe you or BnB
Cancellara could. If it was straight (or straighter) I would have no issues. Speed itself doesn't scare me; running off the road at 40 does.
1. Anytime I'm over 30 mph on the TT bike I'm keeping my hands near the brakes. I at least want to have a prayer at avoiding a critter or out of control racer.2. At my weight it doesn't matter if I'm aero or sitting up, I will accelerate down a hill. To maintain 35 mph in aero coasting I need to be on a -3.5 grade. To maintain 35 mph in the "drops" coasting I need to be on -4.4 grade. To maintain 35 mph in the "drops" on the same -3.5 I would need to expend roughly 160 watts which is active recovery.
3. I pretty much don't pedal over 28.5 mph in an open road TT event. The energy expended isn't worth it.
Example based on my race rig and weight.
28 mph requires 342 watts, 2.33 miles in 5 min
29 mph requires 376 watts, 2.42 miles in 5 min
30 mph requires 412 watts, 2.5 miles in 5 min
14 mph on a 4% grade requires 347 watts, 1.17 miles in 5 min
15 mph on a 4% grade requires 378 watts, 1.25 miles in 5 min
16 mph on a 4% grade requires 410 watts, 1.33 miles in 5 min
Riding 30 mph v. 28 on the flat saves me 22 seconds and costs me 70 watts. Riding 16 mph v. 14 mph on a 4% grade saves me 41 seconds and costs 63 watts.
Psychologically hitting 30 mph on a flat is nice but on a hilly course it's costing you energy reserves that could be better spent else where. Your mileage will vary by weight.
Last set of calculations. I generate about an additional 30 watts of power in the hoods v. aero. Running the numbers from the bike calculator the point where I need to switch from aero to hoods is dropping below 15.1 mph. If I can increase my power in aero position thru training to drop that to a 20 watt difference, then the point where switching is viable drops to 13.3 mph. That's why I believe it's critical to know what your capable on producing on the bike. There's no since fighting the mathmatical aspects of the sport.