Well, I actually did the testing with my tweeters, which are Tang Band 25-302SH, one test on the dashboard, and the other test holding it in the a-pillar location, along with the help of my friend, and we both agreed on the a-pillar location because we both felt the sound surrounded us and had more detail, while on the dashboard, we felt like the sound was just coming from the dashboard, though I do have to say it was harsh on the a-pillar location, but only harsh songs like the beginning of Pink Floyd - Time, and Hardcore, on the dashboard, it sounded a bit dull, by the way, these are neutral tweeters, which is my favorite type of sound anyways.
The a-pillars pic will be posted soon, just need to wait for the epoxy to settle in since 15 year old heat drenched plastic is brittle, so had to fix a few things, but it's coming along nicely.