I have an old Dana Wet Rib that also attatches to the lower shoulder straps and carries a water bottle. But the nice thing about the Wet Rib is that it rides lower and thus is cooler to wear in summer.

True my Wet Rib isn't quite as large as the Syncpack but it does hold a lot. PLUS, I have my GPS in the left upper shoulder strap zippered pocket and a small digital camera in the right shoulder pocket. All this puts more weight in the front.

Eric