Your MaxxAir 4400 on your 2021 Alpine 3910RK is still going to operate correctly even without the lid fully opening with the MaxxAir FanMate RV and Trailer Roof Vent Cover # MA00-955002. The lid on your fan only needs to open 50% to allow for the full circulation rating on your fan. You did select the correct vent cover for your fan. view full answer...