Maybe it's just me,but I'd be more leery of using an ivory joint to break with,than the ivory ferrule.
So far in my experience,unless you have Larry Nevel-type power in your break,masse a LOT of balls where the tip drives into the table,or something else out of the ordinary,you almost can't break a capped ivory ferrule.
From what I've seen in 20 years around this stuff,almost every ivory ferrule that I've seen cracked or flat broken was caused by one of 2 things.
Weather care,where it got too hot or cold (cold is worse here),or a tip that either wasn't protected with a pad or had a tip that was down to 1/32 sidewall thickness.
I saw a guy come into one of the Memphis rooms with an old SW,with an ivory ferrule on one of the shafts. This cue was stored in a soft case,but had been in a VERY cold car for a few hours. The 2nd ball he hit left the table covered with probably 500 small,very sharp shards because the ferrule literally exploded.
The thin tip was caused by a player laying into a hard draw shot,and miscuing. A good sized piece of the ferrule came out of the side of the cap.
I'm not trying to refute those here than know more,just offering a different perspective. Tommy D.