Well I liek yourself hate seeing tweeters sticking out. When I installed my flushmounts I put 'em in my door panels. Don't know what it does acoustically though. Mine could swivel so I just swiveled them up and back towards driver/passenger. Don't knwo if that helps acoustics lol.
Or you could find door panels that had the tweeters stock in them and swap them out. I guess that would be harder though.
Or you could find door panels that had the tweeters stock in them and swap them out. I guess that would be harder though.