Hey Harold, I just checked out your website, very nice. We seem to share a few interests, I was just wondering what kind of smoker ya got. Reason being, I don't recomend the fat cap up if it is a chargriller, or charbroil, or brinkman w/ SFB. The reason is, the heat comming out of the side fire box is usually a little to extreme,I still have my charbroil silver, but don't use it too much any more. I have modified it quite a bit, but I think I would still do the butts, fat cap down in it. The reason I can do them up in the Lang, is because of the reverse flow, and it takes alot of the heat and distributes it pretty evenly. The hottest spot is still right next to the firebox, but it isn't quite as extreme, and I have about 4-5 ways to change it by elevating the tongue of the trialer, changing my log location, changing my damper settings on the fire box, taking some direct heat off by opening up the warmer and its damper...ect.
So Its just my opinion, if ya got one of them cheaper horizontals( no disrespect to anyone who owns them, I have one and like it very much) with a side firebox, or even one without a fire box, I would recomend you still doing the butt cap down. Hate to see ya make a good butt tough or burnt.
Keep enjoying the site Harold, and be sure to let us know how that smoke turns out tomorrow!