Resolving a bad charging issue is easier than you think. First, when you're only getting 12.2 to 12.7, presumably on a dash volt gauge, you should get out of the car, open the hood, put your VOM on the output at the alternator, or on the wire as close as you can get to the alternator output, and measure the voltage there. Then, go here
Alternator wiring..... and read the testing protocol. It could easily be something as simple as voltage drop between the alternator and the load.