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Next, you need to understand the different types of offsets and how the heat flows in them.
1. A traditional flow "open pit" design has no baffle at the throat opening between the fire box and cook chamber, and does not use tuning plates of any kind. This will be a top down cooker, as the heat comes up out of the throat and goes over the top of the food. Fat cap up works best in this type of cooker. This is what your NB smoker is as stock. The Oklahoma Joe Highland/Long Horn is another inexpensive example of this type.
2. A Traditional flow with a downward baffle at the throat (as what you are looking at) will be a bottom up cooker, as the heat is directed down by the baffle and is deflected to the center of the cook chamber where it rises. This may or may not cause a hot spot in the center of your cook chamber. Fat cap down works best in this type of cooker. The Old Country Pecos/Brazos, and the Workhorse Pits 1957/1969/1975 are examples of this style.
3. A traditional flow with a downward baffle and tuning plates will also be a bottom up cooker. The baffle directs the heat down, and it flows under the tuning plates, coming up from the spaces between the plates (or in some cases the holes in a one piece tuning plate). Fat cap down also works best in this type of cooker. The Lone Star Grillz cookers are examples of this style.
4. A reverse flow has a solid baffle that runs from the firebox side to the other end. The heat and smoke run under the baffle to the other side where it enters the cook chamber and moves over the food. This type of cooker is kind of a hybrid, because you have convective heat flowing top down over the food, but you have a significant amount of radiant heat coming up from the reverse flow plate hitting the bottom of the food. Fat cap down works best in this type of cooker because of the strong radiant heat directly under the food from the reverse flow plate. Shirley Fabrication and Lang are examples of this style cooker.
Figure out how you like to cook, and you will figure out what type of cooker will work best for you, which will then answer your question on if that baffle will be a good idea for you, or a bad idea.
When I bought my first offset I screwed up because I did not really understand any of what I describe above. I bought a reverse flow cooker which I later realized is a bottom up cooker best suited for fat cap down..... but I prefer to cook brisket and pork butts fat cap up. The pork butts were a little crispy on the bottom but still turned out OK since they were shredded anyways, but my briskets just never really turned out right.
I now have a traditional flow open pit (Big Phil's Blue Smoke Smoker), which is a top down cooker and my briskets and shoulders come out amazing. Mine has a removable Mill Scale/Franklin type baffle which technically means I have added a baffle (although I can take it out any time), but this style baffle still causes the heat and smoke to flow up over the food, so still a top down cooker. Below is a picture of this type of baffle (not mine, this is actually member TheHojo's, but mine is identical). This is also the same baffle concept mentioned earlier in this thread by member Sandro.
Moral of the story... knowing what you like to cook and how you like to cook it, and having the right type of cooker to cook that way and work WITH you instead of against you makes all the difference in the world.
