The zippy packs are often larger than rated but no matched well as you have noticed.
I.e. You may get a pack that looks like this:
I can routinely extract near 6Ah from my 5Ah packs but they go terribly out of balance near LVC.
The trick is to use the BM6 or equ. and stop when the very first cell hits LVC, then when you charge back up they will balance on their own.
But lets be clear - I always get at least the rated value out of the packs, NEVER less.
EDIT: I forgot to mention - always run them in parallel at the cell level! This balances them out much better!
4 Zippy 6S 5000mah 15C packs - 6 months
4 Zippy R 6S 4150mah 20C packs - 1 year
5 Zippy R 6S 4900mah 20C packs - 1 year
The Zippy R's have seen over 1,500 miles of hard, no current limit, 5305 riding. 150A launches all the time. They are showing their age but I have extracted every last penny of value. Early on I would only balance them every 5th charge and I did not use cell level LVC.
The 15C Zippy packs are, oddly, even better than the Zippy R packs. I ran them all the way down to 2.1V /cell once (left the controller on ) and the next day I charged them back up at 2C and it was like nothing ever happened. They are very stiff and hold flat all the way to LVC.
btw: Charge all of them at 2C.
You can not miss with any of these packs. Buy first, ask questions later.