In reply to The Potato:
TT riders sit on the front of their saddles, hence the expression "on the rivet" for somebody who is giving it some beans. I'd guess that the position is bearable for the duration of a TT because so much body weight is being taken by the legs working at top power.
For a leisure rider, surely the best position is "what's comfortable"? You could mess around with your saddle postion using all the usual rules like the front axle being out of sight below the bars when your position is correct but your muscles will have grown used to your position and even tiny changes will feel strange for a while.
FWIW I have a Specialized Roubaix, which is a pure endurance bike, and a Bianchi Specialissima, which is a lightweight climbing bike. The sitting positions couldn't be more different but over my standard little private TT circuit from home there is little difference in the overall speeds, the Spesh is faster down hills as it's heavier and more aero but the Bianchi is slightly faster on average as it's 3 kgs lighter.