I just wanted to point out, that unless there has been a big change in the judging, in competition your vehicle is judged from both front seats at the same time so it needs to image well for both front listeners. Equalizing the path length's and using time/intensity trading is almost mandatory to accomplish this. Any use of delays would need to be made for both sides, such as delaying a rear mounted sub only.
Now if you don't mind the passenger side sounding like the balance control is turned to the left, then you open up a whole lot of mounting locations. You could mount your mids and tweets on top of the dash and have them aimed right at you. Just like this:
Then all you need is to delay the left mid/tweet and BAM!. Realistic soundstage, assuming you don't make any big mistakes.
The reason you don't see this in competition cars much is because you would lose points for passenger imaging. The guy above is Earl Zausmer. He wasn't a conformist. He didn't care so much about points, he just wanted the best sound to
his ears. As one of the few people to demo his car, I can say it sounded awesome.