Don,
   Not only does the door seal make it much quieter, but if you don't have
it, you'll have cold air swirling in around the door.  Wait'll you feel that
on your flying arm on a cold winter day!
   I don't know how your door to door frame gap got so tight, but I think
you'll want to do whatever it takes to put that seal in once you fly without
it.  Wish I could offer some advice on how to do it at this point, but I
can't think of an easy way to go about it.
   Skip Slater
   N540ES