Originally Posted by
chaadster
No matter; I'd say try sliding your saddle back a bit (yes, could be raised, too) and lowering your bars. If lower bars don't work, try a longer stem of the same rise, so you get more stretch, which will allow you to push your butt back and roll your hips forward more, again flattening the back.
Admittedly, I know nothing of rando riding, but doing 70-80 miles per ride of aggressive, fast riding should be no problem, yet that's quite a bit different than 300km! Are people really riding 300km in a single ride? That'd take like half the day, literally! That's crazy. I've ridden 8hr days, on dirt, but 12-14hrs? Nuts. Anyway, I'll defer to those experienced in randonneuring if that's the case.
One of the great parts about randonneuring is that it challenges what you think you know about bike fit, gearing, saddle choice, nutrition, hydration, attitude, and a whole host of other things. And what works for a quick group ride or century might not work so well toward the end of a 300k or longer ride. So it's all about listening to your body and making adjustments, even if they seem counter to what you were convinced of before. I've heard randonneuring equated with problem solving, and couldn't agree more.