I think if it was me, impatience would overcome my scruples and I would use the other charger with caution. You won't need to raise the low cells to the full 4.2 volts to see whether you have increased the range. If you raise them to something like 4v, you should see a much longer range from the pack, so you will have confirmed that you are on the right track.
Saneagle also said to pay attention to whether the low cells start to rise in voltage, because if they don't they will be heating up. You could solder some extra tail leads to your small plug that you made up so you can monitor the voltage rising as you charge. That way you can charge and keep tabs on how things are going at the same time.
Saneagle also said to pay attention to whether the low cells start to rise in voltage, because if they don't they will be heating up. You could solder some extra tail leads to your small plug that you made up so you can monitor the voltage rising as you charge. That way you can charge and keep tabs on how things are going at the same time.