Heater Flaps

I’ve got the dash stripped out to put some sound insulation on the bulkhead. While it’s out I’m thinking of trying to improve and tidy up some things. Looking at the lower heater flaps, they don’t seal around the edges and also don’t fully cover the aperture. I’m thinking of gluing a piece of closed cell foam on to them, but I’m wondering if it’s supposed to be like that to let some residual heat into the footwell when they are closed. And thoughts ?

I did just that, stuck on 5mm of closed cell foam ...