From what I have learned by my mistakes.
Burls take a long time to dry out. Sometimes as much as 3-4 years depending on size.
Don't cut them up untill they are dry. They will check badly to the point of uselessness.
Sometimes they are full of voids.
It's a bit of a crapshoot harvesting burls, but when you get a good one it's well worth it.
I used to wonder why stabilized burl slabs are so high priced. Now I know!
Hope I didn't spoil your St Judes. I am not an expert on this subject, just my experiences.