Dear NotStar,
What exactly was the point of putting different rsa keys in the new vs old boxes. The new ones are no more secure than the old. The firmware of both is quite old really & the keys/algo have been known for quite some time.
Try embracing card sharing (within a household) & the use of 3rd party equipment. These are not your enemy, stop wasting money on counter measures against these & give a better more flexible service instead!
Seems you are throwing away your older boxes (& money with them) when your new ones don't offer much more & are certainly not more secure. Upgrade your old boxes & send out new cards (not cs crippled please).