Hetfield,

I would recommend putting the tweets right where Ren has them designed with most 6.5-7" drivers. You could put an additional crossover in place and run some small diameter tweets in the a-pillar to cover the not so critical 7khz and up range. It will do a decent job of raising the soundstage while retaining good imaging.

"If you are flammable and have legs, you are never blocking a fire exit" -Mitch Hedberg