First of all are you running 2.2.3 or 2.2.3.2 if you are using any of the two then you can already find strs that allow you to change the probability rates.
For 2.1.6 none are currently out but it won't take much to revers the 2.2.3 or 2.2.3.2 strs to find the offsets in 2.1.6. If people are still getting +7s chances are they are packet manipulating and you have to block the packet ( i don't know what packet before you ask) or implement client side protection.
That is true but i don't think the guy will edit thousands of items client/server side to 6 slots. Probably could do it faster with some sort of hex editing mass replace but that might not be good.