Rolls of foam weather strip are the speaker installers best friend.
RTV works too, but it's more of a permanent fix.. and can be messy if you do not wait for it to cure before you move the panel around.
I used Silicone/RTV to seal up my sub box, then packed it with pillow stuffing to kill standing waves, and make the small sealed box act more like a larger one by slowing down the sound waves through the packing. (There is nearly a full king sized pillow case stuffing in my sealed sub.. and it works GREAT.)
On the doors, I used 4" Diamond seperates, and mounted the tweeters up in the door panels. To fit the larger/deeper than stock mids, the plastic boxes had to be trimmed with a high speed grinder, and if your careful, they do not rattle. The speakers were then given a ring of foam around each at the point where they seal up to the box, and checked for any air leaks or gaps. I then sealed them up around the edges with RTV, and let it cure overnight before putting the boxes back into the doors. I also upgraded the wires, and sealed up where they pass into the boxes too.
To make the stock small front door boxes seem larger, they were packed with pillow stuffing too. To make sure the magnet does not make noise, I ran a few strips of foam across the back, where they pushed up against the plastic stock box, and where I had to cut down the box to make them fit, and potentially made the box weaker as very little of the plastic ribs was left where the speaker magnet goes.
Works really well. During heavy bass, and wearing shorts, I can feel the air ports moving air at my legs, at first I thought it was a bug crawling on me..
LOL
No rattles from the interior of the door.