Speedlites aren't meant to do several back to back high speed recycles. Your 7D2 will expose much faster than the flash can maintain. You're asking for more than what a typical flash can do. Now, to make it work more in your favor, you can:
1) Reduce the power output of the flash and increase ISO to make up for it, to allow for really low power, but high recycle flash times.
2) Use an external battery source, instead of just the 4 in the flash (look at the 8~12 battery banks); this will give you a little faster recycle time too and more pops without changing batteries.
3) Use more than one flash to get more output at a low power (not gonna happen on a hotshoe I know).
If you slow down the FPS on your 7D2 and not shoot at the full unleashed FPS its capable of, you can do it more reliably. But you'd have to be at lower power flash output for it to recycle fast enough.
It simply will never recycle fast enough at 1/4th power, 1/2 power, 1/1 power, to keep up with the 7D2's capabilities for FPS.
This is where a high powered monolight comes into play; so that it's low power (1/32, 1/64, etc) is enough output for your needs, but with a blazing fast recycle time. Just won't be on camera most likely so may not be useful for you.