As far as I know IR doesn't come into play until loads get higher than C. Charging should not matter. Higher IR will make the batteries peak at a higher voltage or that is an indicator, but does not change the capacity of the battery.
Our batteries are rated at C or 1 times the capacity. That would be 3300 Ma for one hour. We use that in 5 minutes or a little more. Lower IR lets the power out of the battery.
High IR would let you have 3.3 amps for 60 minutes, Low IR lets us have 33 amps for 6 minutes.
Charaging rate is C or as high as 2C (6.6) amps, so IR should have little effect.