Thanks for the replies. I may not have described the concept too well.

The tweeters would be flush mounted on top of the dash, about 2" behind the base of the windshield, and fire directly up into the windshield, reflecting sound back into the car. My car has a plastic piece there which the windshield defrost comes through, it extends 4"-5" back from the base of the windshield, and goes the width of the dash...I believe only the 98 & 98.5 cars have this piece. This is the piece I don't know how to remove...

I have moved the tweeters around inside the cabin and found this position to sound better in my application than in the defrost covers for the side windows. Clearer and better imaging with a higher sound stage. Plus I think they'll be easier to flush mount there, trying to make this look like it was done at the factory.

Thanks for the help guys...please let me know any opinions on this setup or better ideas that I haven't tried. And if anyone knows how to remove that plastic piece...please let me know.