Which hill descent position is best?

Froome’s position opens the

Froome’s position opens the hip angle up more than the “top tube safe” position, so while the research says Froome’s position isn’t the most aero, it’s almost certainly the fastest for him, probably because he’s able to produce significantly more power in that position.

Froome’s position was honed

Froome’s position was honed at the aero tunnel. That’s the one.

Chris Froome style, spinning,

Chris Froome style, spinning, while sat on the crossbar.