Tweeter Material, Silk, Alum, Tit, etc

Very good additions.  I agree that it is better to do it right the first time.

One way around this too is to use super steep and super precise slopes on the speakers, greatly reducing the overlap.  However those types of crossovers are very rare.  Plus it doesn't completely eliminate lobing.  The only way to do that is with a coincident speaker design.  

Although I'm planning on doing it with my car as my digital crossover has 72 dB per octave slopes.  Lobing shouldn't be a problem.

Steven Kephart

Adire Audio

Got any old Buck Owens and the Buckaroos albums out there?

one other thing to note, you will gain some imaging cues from havine your tweeters up high, as in sail panels, a pillars, dash, but the issues of lobing and phase seem to be harder to correct than simple imaging issues.

You seem commited to your current tweet location, I'd recommend that you at least think about moving them. i have my tweets in my a pillars and it took me nearly ten hours of trial and error to get then aimed phased and attenuated correctly and the passenger seat (ie shotgun) is always complaning about the tweets being too harsh, next time I'll go with kicks. btw I share a great line from somebody on this forum, "Whne you start paying for my audio equipment, I'll  start tuning it to your seat too"

PS

"Those who are willing to sacrifice their basic liberties to assure their security deserve neither."

A phrase coined by that radical liberal Benjamin Franklin.  A wise statement indeed.  And next time I'm down through Bakersfield I'll drop you a line!