Modding doors is actually a lot easier than people think. The hard part is acquiring the many different skills that help with implementation
I think Hertz has a diagram that implies you want the speakers to be aligned equidistant from your ears in a top to bottom format. Which essentially means you're installing them based on a radius. Personally, that's fine if you don't use Time Aligement. If you use t/a then I would suggest using a similar vertical axis for all 3 speakers on a single side. The distance between them won't matter too much if you have flexibility in active cross overs. Otherwise, to mitigate crossover issues keep the mid-range close to the tweeter in the A pillar. Matt's personal install would be the best choice for that. Also, since the speakers are up high, keep them on-axis. But on-axis means your designed your system for a single seat. It won't sound as good to passengers. An alternative to a similar vertical axis would be to put the mid-bass speakers in your doors. If you keep them mono you may not notice any x-over issues as long as you stay around 200hz...maybe 300hz. This will mitigate any issues using t/a on only two channels for the front. However, if you run them stereo then you'll need 4 channels w/ time alignment. A set for the mid-bass in doors and another set for the tweets and mid-ranges to run from.
Sorry if it seems convoluted. Pick out anything from above if you want me to expoundI'm sure Matt and that Carpepoon can help too.
