Thank you for this - one of the reasons I love my Roseau is that when empty, it weighs close to nothing. I think an excursion to the LC boutique is called for ASAP. I love the look and the leather of Penelope, but haven't really given weight issues much thought because most LC bags are so light!
I actually don't find Penelope to be heavy at all. It probably has some weight compared to Roseau, but compared to most leather bags, I find it to be a dream. I love Longchamp leathers for this reason!