Mounting 6x9's in Front of Rear Side Windows?

hey y'all.

this is the box in my trunk.  tight fit but its in there well, and is strapped in place. 

sounds pretty damn good if i say so myself.  would of been nice if it was a bit more punchier, but i am pretty happy with it.

i have the crossover set at 120hz, as i listen mostly to rock.  subsonic filter is off, and bass boost is up just a bit.  i have the gain turned all the way up(before you guys all start freaking)i have a gain remote by the drivers seat which is up about 20-25%.

here is the question.  in one of the pictures you see a small window(one behind the passenger and driver seat) it measures roughly 11"wide, 15"high, and 4-5"deep.  i had to take my 6x9's off the rear deck cause they were flutterin like leaves in the wind from all the air the 2 12's  are  moving.  now i have lost most of my mids as all i have left are my 4' infinities up front.  i would like like to get some of that mid and mid-bass back, by installing the 6x9's in the windows.  

no. i am not buying new speakers , as i have spent enough money already, don't mean to sound rude there.

the depth of the 6x9 is fine and will fit in the window fine, as i will also black out the window first so you can't see from the outside.

it seems pretty easy, as all i will have to do is take the trim out that surrounds the window, cut a piece of mdf to the shape of the opening and screw it in to the trim and put it all back together again.

do you think the speaker  will be to close to the driver or passenger.  the speaker would be about 18-22" behind the head and the same height.

i have also heard that putting a free-air 6x9 in an enclosure  would kill most of the bass out of the speaker.  is this true. 

please, please, please, i don't want to spend any more money

thanks

KINGPIN

i had the 6x9's on the rear deck but there was no box underneath them. they were just free air from the trunk.  they kind of looked like s$%t up there cause there really wasn't enough roon for them without having to cut up the back deck, and even then it was tight. i actually had the 6x9's mounted on a 1"  piece of mdf that hung over the seat a bit.  like i said without cutting the sheet metal deck into pieces they wouldn't fit.  i think originally they were 4x6 or something back there.

kingpin

  I had the same problem with my 80 monte carlo.

 I have three twelves in the same postion as you, the foam baffles forbidden mentioned from XTC did the trick for me.

 I bought mine from crutchfield, not very expensive for the pair. I bought the 4X10 baffles but the have all sizes 4X10 6x9 and most round sizes.