I’m not concerned with the cost of zip ties. I'm concerned with making the bracket weaker by putting another set of holes in it further back. I can't go farther forward due to the mounting hardware, so the only place for a second is toward the back of the bracket. I'm concerned about the integrity of the bracket if I install a second tie and the requisite set of holes. I've got a few hundred zip-ties at home, that's no big deal. Here's a pic that will give you an idea where the second tie would have to go, and maybe help you understand my concerns about making the bracket weaker: