Have tried the beef flap from BJ'S before, and I am starting to like it better than flank. Wife wanted beef tacos, so picked some up this morning. Marinated in a rub that contains JD and achiote paste. Here is the recipe I followed - I had two beef flaps at 3.5 lbs total.
http://www.nuggetmarket.com/recipes/134/jack-daniels-achiote-flank-steak/Veggies in one CI skillet and some cornbread in the other
Nice char on the steaks
Steaks cooked over a couple small chunks of dogwood
Steaks done
These were very good. My wife even commented that this was some of the best beef I have grilled up for tacos. Achiote imparts an earthy flavor and is used a lot in Mexican/Latin American cuisine.