That is all I needed to know add another 1/2 to 3/4 head space and you wont break jars.
The instructions say at least not no more than.
Another remedy is once you get to your processing time is to lower the pressure to by way of burner 5 psi and let it set for awhile like 15 minutes to 30 and then turn it off and let it cool.
I know this isn't in the safe food handling standards but it is over kill not under kill.
The problem is the smaller canners cool off too fast.
The addition of the head space allows more room for air to expand.
The dropping of the temps slowly is like decompressing from diving deep.
Worth