Yeah, you're absolutely right. Not only is it denser, but they carry more of it (due to oxidizer:fuel ratios and to account for boil off in-flight). No idea wha

Yeah, you're absolutely right. Not only is it denser, but they carry more of it (due to oxidizer:fuel ratios and to account for boil off in-flight). No idea what I meant by "lighter"... I'll blame it on a pre-caffeinated state. It is however true that they can vent it pretty quickly though, leaving the only remaining propellant in the bottom tank.