Glad I can help, been a bit harder lately as so dang busy all the time, whewwwwww!
One competitor used to keep a stuffed animal in back and named him rear phil, lol!
The very few comp cars that use rear speakers just use one or two mids, no tweeters and play them at very low levels. A properly built sound system just does not need them.
There is another situation though, some like to have rear speakers for their passengers to enjoy, rear deck, doors, etc, just bad places so a major compromise either way you go but the deck is best audiowise for front listeners and the doors best for rear seat as not having one pounding the back of your head is nice
I use double faced foam tape for a seal, self taping screws to mount it, several, then mat right up over the baffle and then over that with foam.