Well now,Donna is an owner and the family of the inventor,so she gives real good advice.
I'm merely a cook,but I'd say Cookshack is known to err on the conservative side.
I'd increase my loads gradually and keep good notes.
Personally,I'd not worry about that much apple on a butt,but you could be right.
What about your rub?
Moisture will be your biggest consideration,I've found.
If you make adjustments as you experiment,I'd bet you will be pleasantly surprised.