Crossdraw at 11 o'clock is about the most comfortable for most right handers. But that would necessitate changing holsters when you get out. If you're interested in something like that, check out the Carjacker from
Andrews Leather.
The other good option in my opinion is any IWB you are comfortable wearing, but with a relatively more extreme forward cant. This puts the grip at a more natural angle while seated, and tends to be more comfortable.
I don't spend nearly the time in the car you do, but I wear a MacDaniel II (also from Andrews Leather) with about 30%-40% forward cant when I'm going to be in the car more of the day than normal. With a Colt Commander, I find it plenty comfortable.
Good luck with your search,
Bob