My Flyte SRS-3 is a pretty burly aluminum frame that is on the heavy side. I always feel a little lethargic on it at mild speeds of 13-16 mph. Strangely, it seems to become a different bike if I am more fit and ride in the 17.5-19.0 average speed range. I always thought of it as akin to having really stiff suspension on a sport model car compared to the standard model’s softer suspension.

My other aluminum bike, a Cannondale R1000 CAAD3 is also stiff with its straight, burly seat stays. I use Selle Italia Turbomatic saddles on all my bikes & they do a pretty good job of taking the sting out (for the butt region of the 3 contact points) of oversized aluminum’s rough ride.