Audax rides

175kph at the top of the Eiffel Tower means nothing. Ground windspeed is almost always much lower.
true dat. thank goodness.

Wouldn't bother ditching the helmet for wind resistance. It really won't do much. That which you lose on profile will partly be made up for in turbulence unless you have a shiny head.
duly noted. I think it's because I keep looking up and down like the sweaty unfit nodder that I am.

4 hours is OK for 100k although cramps would indicate that you're overdoing it to keep that up for 200k. Sod the tablets, eat real food, you'll enjoy it much more.
I wasn't hungry though. Eating when I'm not hungry makes me feel ill, which is the last thing I want! If I can avoid that by chucking a tablet into a bidon every 70k or so, then I'll definitely do that. That said, 200k is going to be very long, so I'll probably have a big cafe meal halfway round.