I guess this begs the question of "Why do you trim (or not trim) the fat cap from Brisket".
We used to leave it on, now we remove it almost totally.
Seems that if you put rub on thick fat, it just melts away with the fat. That leaves bare (unspiced) meat, or meat with a layer of nasty fat to present the judges or trim off.
If the fat is trimmed, the rub flavor stays on the meat and is "useful".
We get full bark all around the brisket by removing the fat.
Some say the fat cap (if down) will "cushion" the bottom of the meat That very well may be true on cookers where the heat comes from the bottom. However, we cook on a rotisserie, so the heat is swirling all around--coming from everywhere. Works for us.
So, we find that we get a better product by trimming the fat cap off.
An unexpected side effect is that there is much less useless grease rendering off. Cooker is much easier to keep clean.
This is gonna be a matter of personal preference and will probably vary a lot depending on the cooker.
So, this is just FWIW from my perspective.
"Flirtin' with Disaster" BBQ Team (RETIRED)
FBA and KCBS Cook and Judge.
Former owner of a WSM, a Smokey Joe, a Charbroil Commercial gasser (junk), the legendary "StudeDera", a Fast Eddy PG500, and Sherman.
Now cooking with a Yoder YS640
Proud Pellet guy cooking on real wood.