We were probably talking about a smaller Cookshack,where the max temp is 250�,and that will do a decent job of adding smoke and not drying out.
When you get above that,it is difficult to add smoke-if that is a goal.
As mentioned above,a good standing rib should have a good bit of internal marbling and a decent fat cap.
A sirloin tip,often has neither.
The short term high temps,work pretty well with most larger chunks of meat.
Watch the sugar in your rubs,as they will burn.