Hopefully someone will know the answer to my rack dilemma. As you can see in the following picture, if you install a rear rack the metal arms have to reach down very far:
That works for the above setup, where there is a moderate amount of seatpost showing. I need to drop my rear seat lower to where there is about an inch of post showing to accommodate my 8 year-old stoker. As you can imagine, without super long metal support arms that wouldn't be possible.
Another option is a comfort rack that trek makes:
It has a large metal arm that inserts into the "accessory port" that is welded into the back of the frame. Does anyone have this? If so, do you have any idea how far down you can bring your stoker seat?