I just bought a Yepp Mini, and I think that 1.5 inch exposed measurement may be referring to the height of exposed stem needed to fit the attachment. The quill stems on the bikes i'm considering are definitely less than that in diameter, and the Yepp mounting piece fits just fine. FWIW, I agree that you'll likely want something with swept back bars, a decently upright riding position, and the ability to adjust the seatpost so that you can place at least the balls of your feet on the ground when stopped, as it's hard to slide forward off the seat with the kid in front of you, especially if you're shorter and not riding a large frame. Yepp recommends at least 20" between your seatpost and stem for the Yepp Mini.