Is there a good trick to aligning the nylon backing plate that goes on the opposite side of the control horn?

I always seem to get one hole about 1/2 a screw diameter off.
And then I'm hosed and have to resort to hogging out the hole.

Are you pre-drilling the holes before you install the control horn?? Mark where you want to drill the holes at, and then use drill press to drill the holes to make sure they are straight. If you don't have a drill press you can use a carpenters square and a hand drill to try to get it close. Use the square to approximate the angle to drill your hole at.

Ken

Practice and you'll be able to drill those holes straight. I know that's not what you wanted to hear, but to me, that's the easiest mothod. Use a pin vice rather than a Dremel-type tool, it's easier to control. The slower drill speed gives you more time to align the hole.

Dr.1

Also try pushing a pin through the holes while the horn or backplate are in place, dead center. Use a pencil or a philips head screwdriver to make a dent in the center before you drill. This will keep the bit aligned on those critical first few revolutions of the drill bit. Keep it straight by doing what Ken and Dr1 said, or if you are lucky enough to have level gages on your makita, use those.

Practice... Yeah, I know.
I was just hoping there was some clever trick in the collective knowledge pool.
I wonder if it'd be easier if they just made blank backing plates.
Then I'd just drill them myself wherever the bit would fall.

Dr1: We fired up my G-26 on the Sopwith today for the very first time. We choked it, primed it, and God bless it, that engine lit up on the absolute first revolution of the starter. It was a good feeling. Took 30 minutes to run the tank dry while breaking it in in the shop. Another week, and I'll be patrolling the skies looking for you.... [8D]

Just enlarge the holes. The holes themselves do very little as far as holding the horn straight - It's the clamping action of the horn against the backplate that does the real holding. And if you still want a little extra insurance, slip a little medium CA under the horn just before tightening

This can be frustrating. I use the horn as a template/guide to drill the holes. Start by drilling one hole, put a screw in that hole, drill the next, put a screw in and so on and so forth. I attempt to hold the drill perpendicular to the surface. If needed to get alignment, I chase the holes with the next larger drill bit. I agree with Minnflyer the holes themselves are less important then the clamping action of the horn and backplate. Generally, I find two holes will align enough to get screws started. If the third or fourth hole is misaligned, I see how it is misaligned, remove everything and re-drill the hole making a correction for the misalignment.

Once I know I can get the screws started, I remove everything again, cut the covering from under the horn and backing plate, take a T-pin and make many perforations into the wood from both sides of the control surface in the location of the horn and soak this area with thin CA to harden the wood. After the CA kicks-off, I will chase the holes out again and then finally permanently mount the horn.

Actually, the best way I have found to prevent this in the first place is to CA the horn in place, Then drill BOTH holes - One right after the other.

By doing that, you have a much better chance of keeping the drill on the same plane (Horizontal and Vertical Plane, not Airplane) and the holes will line up much better.