The corner pocket maximum at the time (1953 rule book) was 5 1/8 inches. Isn't 5 1/2 close enough?... I do get a chuckle out of all the stipulations being talked about for John Schmidt, when there were basically none for Willie Mosconi. And if there were for Willie, wouldn't we all have started with "it has to be on a regulation pool table"
That rule book also describes the method of block play for championship matches and marking the break and cue ball between sessions. There is no rule that the player cannot practice between playing sessions.