When retracted, the Peragon cover is the most compact retractable design for maximum cargo space. On most models the cover comes out from the front of the bed about 6″ and hangs down into the bed about 10-11″ on short beds and 11-12″ on midsize to long beds.
It still leaves plenty of clearance to the floor of the bed to slide long items like a piece of plywood all the way to the front. The panels require some extra clearance to fold and unfold.
Keep in mind that with a fixed canister style retractable bed cover, that space is permanently consumed for operation. While the Peragon cover requires some bed space to open and close, the design allows for easy quick-release of the entire cover and doesn't permanently consume any bed space like a canister does.