My experience with flats has taught me several lessons -
Always buy Choice, thicker the better cuts with as much fat as possible on top, and as much fat striation as possible on the bottom.
Inject with a phosphate based product (helps promote moisture loss) ButcherBBQ.com has some good options.
Cook fat side down. This protects the lean bottom from drying out.
I used to foil flats. I had great success a few weeks ago by wrapping the meat in a couple layers of brown craft paper when the brisket hit the stall at 165. See THIS thread discussion.
I like to smoke all large meats (flats, packers, pork butts) at 240. I can't advise you on the elevation differencial.
Flats are persnickity which is most of us prefer Choice packers. Now and again you'll get one that will come out great with a simple salt and pepper seasoning, no wrapping, etc. but the odds aren't in your favor, which has led me to develop the tweaks mentioned above.
Read Smokin's 101, keep notes. Good luck.