Walton,
If you insist on using the Rocket city hardware you will have to drill at least a 1/2 hole through the control surface to accept a hardwood dowel, then tap the dowel for an 8-32 thread and thread in your rod. Oh,,, make sure you glue in the dowel. There is no such thing as a hard spot on the top and bottom Again, the hardware that comes with the kit is much more than adequate but if you want to go to the trouble for the heck of it, be my guest. Obviously you have heard someone somewhere mention that this is a good thing to do. That's the trouble with some guys spouting off about what works and what doesn't. You're obviously a newbie with little experience in large aircraft to be asking the question you did in the first place. My advice is to use what came with the kit and leave well enough alone.

By the way. There is no need to use the back up plate that comes with the kit. The screws supplied aren't long enough anyhow. Find the mounting position, drill 1/16th inch holes where the screws will go and fill with thin CA and then just put your screws in. You will rip the control surface apart before you ever pull out one of those horns mounted in this fashion. Good luck

OH.....I almost forgot...If you drill the dowel holes wrong or tap the hole for the rods wrong you will have problems with the geometry of your new horns. The holes must match perfectly or get ready for some set up fun when you connect your servos.