My quite normal 531 frame from the early '90s (54 cm) weighs about 4.9 lb plus 0.75 lb for a carbon fork and I still can bring a complete bike in at 16.25 lb without pedals, cages, or computer mounts. I have FSA SL-K Light crank, Rival shifters and derailleurs, Zero Gravity brakes and a pretty lightweight cockpit. Clincher wheels weight under 1,300 g. So a modern steel frame and fork that weigh 1.5 lb less would be no trouble to bring in on a full build at under 15 lb. Red stuff would make the bike even lighter.