Don't change a thing... the screws are long enough to bite all there is to bite and make sure to mark the position of the horn and pilot drill the 3 holes.

Then cut a triangle of covering away using the holes as the points
Medium or thick CA the horn to the bare wood
Install the screws, remove, harden the holes with thin CA, let CA cure 15 minutes, re-install screws.


On the linkage of the ailerons, there will be binding if you mount the horn square and out in line with the outer hole of the servo arm. THis will result in the MOST amount of binding...

Instead, mount the horn in line with the side of the servo, and slightly angle the horm to align with about halfway out on the servo arm. WHat this does is "split the difference" of the binding and makes it a non issue.

Oh and mount the srvos with the sahfts furhtest away from the horn... this will make the linkage as long as possible and again help minimize any binding...

Others who have mounted it square have complained of popping out the ball bearing in the horn... and others pop it out themselves and install a ball link... my method has worked perfectly....

And the horns are ROCK solid in some VERY hard walls, blenders, elevators, snaps... etc....