Instead of asking people what would be our best guess I suggest you to use double side tape and put the tweeter in all different locations that you think they will sound ok and properly (for you).
Put it in loc. 1 and play some music and lesson for all difernet seating locations at your car (specially front, both seats), then do the same with location 2, etc, etc.
Once you have a choice then make the final installation.
One quick advice is that most of users found speakers "harsh" which most of the time I have found that most likely it's a poor installation. You have no idea of how important installation is over a system, a regular component can put a high end component to shame if is under good installation. I have seen people complain about their $$$ expensive components not perform well but all comes out to installation (keep this in mind).
One trick is that midbass woofer has to be as close as possible to the tweeter, we often make some mistake and put the woofer in stock location and tweeters up in the dash, or side mirrors, etc. and this make your ears caught high frequencies closer than the low freqs. and that's when we think a comp. is harsh and anoying but in my experience I can tell you most of the time is about installation (of course metal tweeter are brighter than silk, don't want to go deep on that), and also the tweeter attenuation plays a big role since sometimes we put speakers at 0 since they came shipped like that (but is important to play with this also).
Remember, whenever a manufacturing is designing a component, they are only guessing where the tweeter will be mounted in relation with the woofer and the drivers (lessoners) position.
Sorry for going long and write you a book, but I hope this info can help you.
