You're on the right track, for sure, Gene! I go fat cap up on butts, but it really doesn't matter to me. Most of the butts I get are pretty-well trimmed, and most of the "beneficial" fat is really internal anyways. I also don't think 235 will hurt, either. I use 225, but usually kick it up to 235 once it works through the stall and the temp starts climbing again. All the "tenderizing" cooking is done, at that point, so a little extra heat doesn't hurt a bit. Some do butts at 240, or higher, but I like 235 and below.
Let us know how it turns out! (With pictures, please!)