Can I move my return air vent?

The original return vent was installed in a wall that was removed. The vent in the wall went down into the floor between to joists. These joists were sealed off by a sheet metal bottom. The original design had an additional joist installed for this vent so the actual joist spacing is about 8" wide in this area. I'd like to know if I can move the original position of the return vent in the room it was in, and connect it to the floor joists using flexible tubing? The room I'm talking about was L shaped when the wall was up. Now that it's removed, the room only has a middle wall that seperates the Kitchen from the living room. Theres a return vent in that middle wall. It's only about 10 feet away from where the vent I removed was, and I think it feeds the same duct in the floor.