Below is a link to Carlos Sastre following Andy Schlek and a pic of Lance. They are GC guys. GCs are into power and comfort. Their job is to win a grand tour by conserving energy and using their power at the right moments in time. They are not breakaway artists and if they win a stage it is in the mountains usually with a mountain top finish.

My point is not to compare you (or I) to these guys but to note the set up that is used by the best in the business for max power and IMO comfort and not necessarily aero. Note the longer stems, shorter head tubes and arm positions with respect to the body. IMO, one would increase the hip angle, away from the bar, (forward bend) to match ones hamstring and back flexibility and core strength. In my retul fitting my coach suggested I go from an 9cm stem to an 11cm stem. He put them on the bike so that I could feel the difference. He said the 9 cm was okay but the 11 cm was better. The 11 cm felt great but I am conservative and concerned about changing my hip angle and subjecting my back to more stress. I have thought about an ergo stem where I could change it 1mm a month. I know I could adapt to that.

With respect to one bike being okay for long rides and the other not, I suspect it is about stiffness. I think a stiff carbon frame (assume that is what a Tarmac is) is great for a strong powerful rider with great core and back strength. For longer rides and weaker riders (me), I think a more forgiving frame is better. If I were going to do longer rides (greater than 60 miles), I would ride Ti or steel and not worry about a pound of frame weight. If I were ever so lucky to make it to a Cat 2, I would be able to ride on a 2X4 mounted on a solid plastic frame for 100 miles.

http://www.google.com/imgres?imgurl=...KZuetgOeyOmrAw