I run both on my Silver Birdy (and Emerald Birdy for that matter).. use it almost daily .. I think it's a terrific option.. bag can expand if needed for thicker objects.. easily fits a laptop .. holds lots of groceries .. it gets lots of use.. having it mounted to the seatpost doesn't adversely affect handling much .. I've had quick release baskets mounted to the handlebars, but much prefer the Crossrack items..and if you have two Birdy bikes (as I see you do), you just move your load carrying abilities from bike to bike with one quick release..