...would it be safe to say that as a rule of thumb when using stop market orders that a stop price at 10-15% below the days low (for that particular equity in play) be acceptable?
Now, Bull, you touch on the really difficult aspect of stops: where to put them. Setting a stop is much more an art than a science, particularly when playing very short time frames. Much depends on the particular stock and its "personality", the time frame for your trade, the calculated risk/reward going into the trade, and your tolerance for pain. I'm afraid my response is not going to be much help to you, but this is a subject more fitting for a book than for a single post.
Sandy