50 haks from 30 minnows isnt a 60% break rate...its a 37.5% break rate... which is about in line with what I tend to get. I find it varies anywhere from 25-40%
Side note, I tend to use sinking minnows over minnows.
http://ffxi.gamerescape.com/wiki/Hakuryu#Fishing
Did a lil testing way way back, haven't updated in months.
Also, sinking minnows are the best over time, at least during my testing. Just makes sense since there are less fish biting.
Also I think that sinking minnow snap rate is higher, but only like 2%. I would have to do thousands more to know ~1% and I just didn't keep up with recording it.
But I believe with the rings you have ~5% more hakuryu using sinking minnow vs just minnow