Hangar 9 P-51 Mustang ARF Assembly Manual page 16

Section 3: Installing the Aileron Linkage
 
Step 5
Attach the clevis to the outer hole on the control horn.
Place the horn flat on the aileron, aligning the linkage
parallel to the edge of the servo cover. Use a felt-tipped
pen to mark the location for the three control horn
mounting screws.
 
Step 6
Use a 5/64" (2mm) drill bit to drill the locations for the
three screws. Use care to drill all three holes parallel to
each other.
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 
Step 7
Use a T-pin to poke holes through the covering in the area
inside the triangle made by the three holes. Poke holes in
the covering on both the top and bottom of the aileron.
 
Step 8
Apply a small amount of thin CA in the area made by the
holes in the following step. A few drops of thin CA into
each hole is also required. This hardens the balsa, giving
the control horn a much more solid surface to mount to.
Do not use accelerator to allow the CA to penetrate into
the wood.