Best Location for Aftermarket Tweeters

[B6T]

Hi everyone,
I'm in the middle of installing a new stereo system in my '03 Boxster S. The car was equipped with the upgraded Bose stereo. I'm replacing the factory CDR-23 headunit, Bose amp, and all speakers. I've chosen to do this because of the incompatibility of the fibre-optic driven/MOST bus factory amp with aftermarket head units, and the subsequent incompatibility of the factory speakers with aftermarket amps.

I'm installing a double-din Pioneer headunit and a 4-channel Alpine amplifier. I'm replacing the 5.5" drivers in the rear Bose enclosure with the same size of speaker except in the correct ohm rating for my new amp. I'm abandoning the small 3" mids in the enclosure. Up front, the upper dash co-axial speakers and door mounted subs will be replaced by a set of Infinity kappa series 5.25" components. I will mount the woofer of the component set in the existing door enclosure in place of the Bose 5.25" speaker. The upper dash speakers will be eliminated.

My question is where would the best spot be to install the component tweeters. I know I'm changing around the sound stage by eliminating the mids in the rear speaker box and the upper dash co-axials, so I want to ensure that I put the tweeters in the best spot for balanced sound.

I was thinking about 3D printing a panel for the tweeter and placing it in the spot once occupied by the upper dash speakers. But I'm not sure if this will make the sound distorted because it relies on reflection off the windsheild or too 'bright' because a closer proximity to the listener relative to the lower mounted speaker in the door.

What is your experience and recommendations?

Thanks.

(I also posted this on Rennlist)