Flex pcb stiffener and soldering access?

Hi,

We're designing a flex PCB that's got soldering needs on both top and bottom sides, especially for the below USB connector. Notice the SMT pads for top side soldering and the TH pads for bottom side soldering. We need to include a stiffener to give mechanical strength for the connector, but since the connector and SMT pads are on the top side the stiffener cannot be on the top side, which means it needs to be on the bottom side. So if the stiffener is located on the bottom side then how do we design the stiffener so that there's easy access for the bottom side flex pcb TH pads soldering? Can you show some pics of similar examples or suggestions on how to do this?

Thanks