if all the cells are in series, (which it looks like they are), then your maximum 2C charge rate is 2.8A.... It looks like maybe it's split into 2 stacks, but each stack is still in series, so each stack could be independently charged at 2.8A as well. I would probably have the charger charge as a whole pack until it's around 16.4-16.6V for the pack, then have it go into balance mode and finalize things
keep in mind that if you were to wire up the cells in parallel, for say, a 5.6AH pack, your maximum charge rate would be the 11.2A, but it would still take the same amount of time as charging the series pack at 2.8A. (It would take approximately 30 minutes for 11.2 Amps to "fill up" a 5.6AH pack, it would take approximately 30 minutes for 2.8 Amps to "fill up" a 1.4AH pack, the same amount of watts move in both cases, but in one case you move more watts through higher line pressure (more voltage) and in the other through more flow)
As you already know, when you wire in series, the pack gains voltage, not capacity, when you wire in parallel you gain capacity not voltage, always calculate the packs capacity, and then figure out your charge/discharge rates based on the C rating for the cells in question.
